diff --git a/juce_amalgamated.cpp b/juce_amalgamated.cpp
index 355c5cd6e1..30139fd987 100644
--- a/juce_amalgamated.cpp
+++ b/juce_amalgamated.cpp
@@ -2341,7 +2341,13 @@ AbstractFifo::~AbstractFifo() {}
 
 int AbstractFifo::getTotalSize() const throw()		{ return bufferSize; }
 int AbstractFifo::getFreeSpace() const throw()		{ return bufferSize - getNumReady(); }
-int AbstractFifo::getNumReady() const throw()		 { return validEnd.get() - validStart.get(); }
+
+int AbstractFifo::getNumReady() const throw()
+{
+	const int vs = validStart.get();
+	const int ve = validEnd.get();
+	return ve >= vs ? (ve - vs) : (bufferSize - (vs - ve));
+}
 
 void AbstractFifo::reset() throw()
 {
@@ -2359,10 +2365,10 @@ void AbstractFifo::setTotalSize (int newSize) throw()
 void AbstractFifo::prepareToWrite (int numToWrite, int& startIndex1, int& blockSize1, int& startIndex2, int& blockSize2) const throw()
 {
 	const int vs = validStart.get();
-	const int ve = validEnd.get();
+	const int ve = validEnd.value;
 
-	const int freeSpace = bufferSize - (ve - vs);
-	numToWrite = jmin (numToWrite, freeSpace);
+	const int freeSpace = ve >= vs ? (bufferSize - (ve - vs)) : (vs - ve);
+	numToWrite = jmin (numToWrite, freeSpace - 1);
 
 	if (numToWrite <= 0)
 	{
@@ -2373,26 +2379,30 @@ void AbstractFifo::prepareToWrite (int numToWrite, int& startIndex1, int& blockS
 	}
 	else
 	{
-		startIndex1 = (int) (ve % bufferSize);
+		startIndex1 = ve;
 		startIndex2 = 0;
-		blockSize1 = jmin (bufferSize - startIndex1, numToWrite);
+		blockSize1 = jmin (bufferSize - ve, numToWrite);
 		numToWrite -= blockSize1;
-		blockSize2 = numToWrite <= 0 ? 0 : jmin (numToWrite, (int) (vs % bufferSize));
+		blockSize2 = numToWrite <= 0 ? 0 : jmin (numToWrite, vs);
 	}
 }
 
 void AbstractFifo::finishedWrite (int numWritten) throw()
 {
 	jassert (numWritten >= 0 && numWritten < bufferSize);
-	validEnd += numWritten;
+	int newEnd = validEnd.value + numWritten;
+	if (newEnd >= bufferSize)
+		newEnd -= bufferSize;
+
+	validEnd = newEnd;
 }
 
 void AbstractFifo::prepareToRead (int numWanted, int& startIndex1, int& blockSize1, int& startIndex2, int& blockSize2) const throw()
 {
-	const int vs = validStart.get();
+	const int vs = validStart.value;
 	const int ve = validEnd.get();
 
-	const int numReady = ve - vs;
+	const int numReady = ve >= vs ? (ve - vs) : (bufferSize - (vs - ve));
 	numWanted = jmin (numWanted, numReady);
 
 	if (numWanted <= 0)
@@ -2404,20 +2414,127 @@ void AbstractFifo::prepareToRead (int numWanted, int& startIndex1, int& blockSiz
 	}
 	else
 	{
-		startIndex1 = (int) (vs % bufferSize);
+		startIndex1 = vs;
 		startIndex2 = 0;
-		blockSize1 = jmin (bufferSize - startIndex1, numWanted);
+		blockSize1 = jmin (bufferSize - vs, numWanted);
 		numWanted -= blockSize1;
-		blockSize2 = numWanted <= 0 ? 0 : jmin (numWanted, (int) (ve % bufferSize));
+		blockSize2 = numWanted <= 0 ? 0 : jmin (numWanted, ve);
 	}
 }
 
 void AbstractFifo::finishedRead (int numRead) throw()
 {
-	jassert (numRead >= 0 && numRead < bufferSize);
-	validStart += numRead;
+	jassert (numRead >= 0 && numRead <= bufferSize);
+
+	int newStart = validStart.value + numRead;
+	if (newStart >= bufferSize)
+		newStart -= bufferSize;
+
+	validStart = newStart;
 }
 
+#if JUCE_UNIT_TESTS
+
+class AbstractFifoTests  : public UnitTest
+{
+public:
+	AbstractFifoTests() : UnitTest ("Abstract Fifo") {}
+
+	class WriteThread  : public Thread
+	{
+	public:
+		WriteThread (AbstractFifo& fifo_, int* buffer_)
+			: Thread ("fifo writer"), fifo (fifo_), buffer (buffer_)
+		{
+			startThread();
+		}
+
+		~WriteThread()
+		{
+			stopThread (5000);
+		}
+
+		void run()
+		{
+			int n = 0;
+
+			while (! threadShouldExit())
+			{
+				int num = Random::getSystemRandom().nextInt (2000) + 1;
+
+				int start1, size1, start2, size2;
+				fifo.prepareToWrite (num, start1, size1, start2, size2);
+
+				jassert (size1 >= 0 && size2 >= 0);
+				jassert (size1 == 0 || (start1 >= 0 && start1 < fifo.getTotalSize()));
+				jassert (size2 == 0 || (start2 >= 0 && start2 < fifo.getTotalSize()));
+
+				int i;
+				for (i = 0; i < size1; ++i)
+					buffer [start1 + i] = n++;
+
+				for (i = 0; i < size2; ++i)
+					buffer [start2 + i] = n++;
+
+				fifo.finishedWrite (size1 + size2);
+			}
+		}
+
+	private:
+		AbstractFifo& fifo;
+		int* buffer;
+	};
+
+	void runTest()
+	{
+		beginTest ("AbstractFifo");
+
+		int buffer [5000];
+		AbstractFifo fifo (numElementsInArray (buffer));
+
+		WriteThread writer (fifo, buffer);
+
+		int n = 0;
+
+		for (int count = 1000000; --count >= 0;)
+		{
+			int num = Random::getSystemRandom().nextInt (6000) + 1;
+
+			int start1, size1, start2, size2;
+			fifo.prepareToRead (num, start1, size1, start2, size2);
+
+			if (! (size1 >= 0 && size2 >= 0)
+					&& (size1 == 0 || (start1 >= 0 && start1 < fifo.getTotalSize()))
+					&& (size2 == 0 || (start2 >= 0 && start2 < fifo.getTotalSize())))
+			{
+				expect (false, "prepareToRead returned -ve values");
+				break;
+			}
+
+			bool failed = false;
+
+			int i;
+			for (i = 0; i < size1; ++i)
+				failed = (buffer [start1 + i] != n++) || failed;
+
+			for (i = 0; i < size2; ++i)
+				failed = (buffer [start2 + i] != n++) || failed;
+
+			if (failed)
+			{
+				expect (false, "read values were incorrect");
+				break;
+			}
+
+			fifo.finishedRead (size1 + size2);
+		}
+	}
+};
+
+static AbstractFifoTests fifoUnitTests;
+
+#endif
+
 END_JUCE_NAMESPACE
 /*** End of inlined file: juce_AbstractFifo.cpp ***/
 
@@ -4948,7 +5065,12 @@ public:
 			visitor.useSymbol (Symbol (scope.getScopeUID(), getSymbol()->symbol));
 
 			SymbolVisitingVisitor v (right, visitor, recursionDepth + 1);
-			scope.visitRelativeScope (getSymbol()->symbol, v);
+
+			try
+			{
+				scope.visitRelativeScope (getSymbol()->symbol, v);
+			}
+			catch (...) {}
 		}
 
 		void renameSymbol (const Symbol& oldSymbol, const String& newName, const Scope& scope, int recursionDepth)
@@ -4957,7 +5079,12 @@ public:
 			getSymbol()->renameSymbol (oldSymbol, newName, scope, recursionDepth);
 
 			SymbolRenamingVisitor visitor (right, oldSymbol, newName, recursionDepth + 1);
-			scope.visitRelativeScope (getSymbol()->symbol, visitor);
+
+			try
+			{
+				scope.visitRelativeScope (getSymbol()->symbol, visitor);
+			}
+			catch (...) {}
 		}
 
 	private:
@@ -5792,8 +5919,9 @@ double Expression::Scope::evaluateFunction (const String& functionName, const do
 	throw Helpers::EvaluationError ("Unknown function: \"" + functionName + "\"");
 }
 
-void Expression::Scope::visitRelativeScope (const String&, Visitor&) const
+void Expression::Scope::visitRelativeScope (const String& scopeName, Visitor&) const
 {
+	throw Helpers::EvaluationError ("Unknown symbol: " + scopeName);
 }
 
 const String Expression::Scope::getScopeUID() const
@@ -61611,7 +61739,7 @@ namespace ComponentBuilderHelpers
 								   const ValueTree& state, Component* parent)
 	{
 		Component* const c = type.addNewComponentFromState (state, parent);
-		jassert (c != 0);
+		jassert (c != 0 && c->getParentComponent() == parent);
 		c->setComponentID (getStateId (state));
 		return c;
 	}
@@ -80376,6 +80504,8 @@ void RelativeCoordinatePositionerBase::ComponentScope::visitRelativeScope (const
 
 	if (targetComp != 0)
 		visitor.visit (ComponentScope (*targetComp));
+	else
+		Expression::Scope::visitRelativeScope (scopeName, visitor);
 }
 
 const String RelativeCoordinatePositionerBase::ComponentScope::getScopeUID() const
@@ -80479,6 +80609,10 @@ public:
 		else
 		{
 			// The named component doesn't exist, so we'll watch the parent for changes in case it appears later..
+			Component* const parent = component.getParentComponent();
+			if (parent != 0)
+				positioner.registerComponentListener (*parent);
+
 			positioner.registerComponentListener (component);
 			ok = false;
 		}
@@ -80511,10 +80645,17 @@ void RelativeCoordinatePositionerBase::componentParentHierarchyChanged (Componen
 	apply();
 }
 
+void RelativeCoordinatePositionerBase::componentChildrenChanged (Component& changed)
+{
+	if (getComponent().getParentComponent() == &changed && ! registeredOk)
+		apply();
+}
+
 void RelativeCoordinatePositionerBase::componentBeingDeleted (Component& component)
 {
 	jassert (sourceComponents.contains (&component));
 	sourceComponents.removeValue (&component);
+	registeredOk = false;
 }
 
 void RelativeCoordinatePositionerBase::markersChanged (MarkerList*)
diff --git a/juce_amalgamated.h b/juce_amalgamated.h
index 5576dd18ad..44c0e0f2b5 100644
--- a/juce_amalgamated.h
+++ b/juce_amalgamated.h
@@ -45966,6 +45966,7 @@ public:
 
 	void componentMovedOrResized (Component&, bool, bool);
 	void componentParentHierarchyChanged (Component&);
+	void componentChildrenChanged (Component& component);
 	void componentBeingDeleted (Component& component);
 	void markersChanged (MarkerList*);
 	void markerListBeingDeleted (MarkerList* markerList);
diff --git a/src/containers/juce_AbstractFifo.cpp b/src/containers/juce_AbstractFifo.cpp
index 534c87da00..46dde69868 100644
--- a/src/containers/juce_AbstractFifo.cpp
+++ b/src/containers/juce_AbstractFifo.cpp
@@ -41,7 +41,13 @@ AbstractFifo::~AbstractFifo() {}
 
 int AbstractFifo::getTotalSize() const throw()            { return bufferSize; }
 int AbstractFifo::getFreeSpace() const throw()            { return bufferSize - getNumReady(); }
-int AbstractFifo::getNumReady() const throw()             { return validEnd.get() - validStart.get(); }
+
+int AbstractFifo::getNumReady() const throw()
+{
+    const int vs = validStart.get();
+    const int ve = validEnd.get();
+    return ve >= vs ? (ve - vs) : (bufferSize - (vs - ve));
+}
 
 void AbstractFifo::reset() throw()
 {
@@ -60,10 +66,10 @@ void AbstractFifo::setTotalSize (int newSize) throw()
 void AbstractFifo::prepareToWrite (int numToWrite, int& startIndex1, int& blockSize1, int& startIndex2, int& blockSize2) const throw()
 {
     const int vs = validStart.get();
-    const int ve = validEnd.get();
+    const int ve = validEnd.value;
 
-    const int freeSpace = bufferSize - (ve - vs);
-    numToWrite = jmin (numToWrite, freeSpace);
+    const int freeSpace = ve >= vs ? (bufferSize - (ve - vs)) : (vs - ve);
+    numToWrite = jmin (numToWrite, freeSpace - 1);
 
     if (numToWrite <= 0)
     {
@@ -74,26 +80,30 @@ void AbstractFifo::prepareToWrite (int numToWrite, int& startIndex1, int& blockS
     }
     else
     {
-        startIndex1 = (int) (ve % bufferSize);
+        startIndex1 = ve;
         startIndex2 = 0;
-        blockSize1 = jmin (bufferSize - startIndex1, numToWrite);
+        blockSize1 = jmin (bufferSize - ve, numToWrite);
         numToWrite -= blockSize1;
-        blockSize2 = numToWrite <= 0 ? 0 : jmin (numToWrite, (int) (vs % bufferSize));
+        blockSize2 = numToWrite <= 0 ? 0 : jmin (numToWrite, vs);
     }
 }
 
 void AbstractFifo::finishedWrite (int numWritten) throw()
 {
     jassert (numWritten >= 0 && numWritten < bufferSize);
-    validEnd += numWritten;
+    int newEnd = validEnd.value + numWritten;
+    if (newEnd >= bufferSize)
+        newEnd -= bufferSize;
+
+    validEnd = newEnd;
 }
 
 void AbstractFifo::prepareToRead (int numWanted, int& startIndex1, int& blockSize1, int& startIndex2, int& blockSize2) const throw()
 {
-    const int vs = validStart.get();
+    const int vs = validStart.value;
     const int ve = validEnd.get();
 
-    const int numReady = ve - vs;
+    const int numReady = ve >= vs ? (ve - vs) : (bufferSize - (vs - ve));
     numWanted = jmin (numWanted, numReady);
 
     if (numWanted <= 0)
@@ -105,19 +115,132 @@ void AbstractFifo::prepareToRead (int numWanted, int& startIndex1, int& blockSiz
     }
     else
     {
-        startIndex1 = (int) (vs % bufferSize);
+        startIndex1 = vs;
         startIndex2 = 0;
-        blockSize1 = jmin (bufferSize - startIndex1, numWanted);
+        blockSize1 = jmin (bufferSize - vs, numWanted);
         numWanted -= blockSize1;
-        blockSize2 = numWanted <= 0 ? 0 : jmin (numWanted, (int) (ve % bufferSize));
+        blockSize2 = numWanted <= 0 ? 0 : jmin (numWanted, ve);
     }
 }
 
 void AbstractFifo::finishedRead (int numRead) throw()
 {
-    jassert (numRead >= 0 && numRead < bufferSize);
-    validStart += numRead;
+    jassert (numRead >= 0 && numRead <= bufferSize);
+
+    int newStart = validStart.value + numRead;
+    if (newStart >= bufferSize)
+        newStart -= bufferSize;
+
+    validStart = newStart;
 }
 
+//==============================================================================
+//==============================================================================
+#if JUCE_UNIT_TESTS
+
+#include "../utilities/juce_UnitTest.h"
+#include "../maths/juce_Random.h"
+#include "../threads/juce_Thread.h"
+
+
+class AbstractFifoTests  : public UnitTest
+{
+public:
+    AbstractFifoTests() : UnitTest ("Abstract Fifo") {}
+
+    class WriteThread  : public Thread
+    {
+    public:
+        WriteThread (AbstractFifo& fifo_, int* buffer_)
+            : Thread ("fifo writer"), fifo (fifo_), buffer (buffer_)
+        {
+            startThread();
+        }
+
+        ~WriteThread()
+        {
+            stopThread (5000);
+        }
+
+        void run()
+        {
+            int n = 0;
+
+            while (! threadShouldExit())
+            {
+                int num = Random::getSystemRandom().nextInt (2000) + 1;
+
+                int start1, size1, start2, size2;
+                fifo.prepareToWrite (num, start1, size1, start2, size2);
+
+                jassert (size1 >= 0 && size2 >= 0);
+                jassert (size1 == 0 || (start1 >= 0 && start1 < fifo.getTotalSize()));
+                jassert (size2 == 0 || (start2 >= 0 && start2 < fifo.getTotalSize()));
+
+                int i;
+                for (i = 0; i < size1; ++i)
+                    buffer [start1 + i] = n++;
+
+                for (i = 0; i < size2; ++i)
+                    buffer [start2 + i] = n++;
+
+                fifo.finishedWrite (size1 + size2);
+            }
+        }
+
+    private:
+        AbstractFifo& fifo;
+        int* buffer;
+    };
+
+    void runTest()
+    {
+        beginTest ("AbstractFifo");
+
+        int buffer [5000];
+        AbstractFifo fifo (numElementsInArray (buffer));
+
+        WriteThread writer (fifo, buffer);
+
+        int n = 0;
+
+        for (int count = 1000000; --count >= 0;)
+        {
+            int num = Random::getSystemRandom().nextInt (6000) + 1;
+
+            int start1, size1, start2, size2;
+            fifo.prepareToRead (num, start1, size1, start2, size2);
+
+            if (! (size1 >= 0 && size2 >= 0)
+                    && (size1 == 0 || (start1 >= 0 && start1 < fifo.getTotalSize()))
+                    && (size2 == 0 || (start2 >= 0 && start2 < fifo.getTotalSize())))
+            {
+                expect (false, "prepareToRead returned -ve values");
+                break;
+            }
+
+            bool failed = false;
+
+            int i;
+            for (i = 0; i < size1; ++i)
+                failed = (buffer [start1 + i] != n++) || failed;
+
+            for (i = 0; i < size2; ++i)
+                failed = (buffer [start2 + i] != n++) || failed;
+
+            if (failed)
+            {
+                expect (false, "read values were incorrect");
+                break;
+            }
+
+            fifo.finishedRead (size1 + size2);
+        }
+    }
+};
+
+static AbstractFifoTests fifoUnitTests;
+
+#endif
 
 END_JUCE_NAMESPACE
diff --git a/src/gui/components/layout/juce_ComponentBuilder.cpp b/src/gui/components/layout/juce_ComponentBuilder.cpp
index 1c944e9e6d..6dfc19c493 100644
--- a/src/gui/components/layout/juce_ComponentBuilder.cpp
+++ b/src/gui/components/layout/juce_ComponentBuilder.cpp
@@ -74,7 +74,7 @@ namespace ComponentBuilderHelpers
                                    const ValueTree& state, Component* parent)
     {
         Component* const c = type.addNewComponentFromState (state, parent);
-        jassert (c != 0);
+        jassert (c != 0 && c->getParentComponent() == parent);
         c->setComponentID (getStateId (state));
         return c;
     }
diff --git a/src/gui/components/positioning/juce_RelativeCoordinatePositioner.cpp b/src/gui/components/positioning/juce_RelativeCoordinatePositioner.cpp
index 5f2f8af420..5bf2097dfa 100644
--- a/src/gui/components/positioning/juce_RelativeCoordinatePositioner.cpp
+++ b/src/gui/components/positioning/juce_RelativeCoordinatePositioner.cpp
@@ -71,6 +71,8 @@ void RelativeCoordinatePositionerBase::ComponentScope::visitRelativeScope (const
 
     if (targetComp != 0)
         visitor.visit (ComponentScope (*targetComp));
+    else
+        Expression::Scope::visitRelativeScope (scopeName, visitor);
 }
 
 const String RelativeCoordinatePositionerBase::ComponentScope::getScopeUID() const
@@ -175,6 +177,10 @@ public:
         else
         {
             // The named component doesn't exist, so we'll watch the parent for changes in case it appears later..
+            Component* const parent = component.getParentComponent();
+            if (parent != 0)
+                positioner.registerComponentListener (*parent);
+
             positioner.registerComponentListener (component);
             ok = false;
         }
@@ -208,10 +214,17 @@ void RelativeCoordinatePositionerBase::componentParentHierarchyChanged (Componen
     apply();
 }
 
+void RelativeCoordinatePositionerBase::componentChildrenChanged (Component& changed)
+{
+    if (getComponent().getParentComponent() == &changed && ! registeredOk)
+        apply();
+}
+
 void RelativeCoordinatePositionerBase::componentBeingDeleted (Component& component)
 {
     jassert (sourceComponents.contains (&component));
     sourceComponents.removeValue (&component);
+    registeredOk = false;
 }
 
 void RelativeCoordinatePositionerBase::markersChanged (MarkerList*)
diff --git a/src/gui/components/positioning/juce_RelativeCoordinatePositioner.h b/src/gui/components/positioning/juce_RelativeCoordinatePositioner.h
index a7bc77f2f1..91fbabcca4 100644
--- a/src/gui/components/positioning/juce_RelativeCoordinatePositioner.h
+++ b/src/gui/components/positioning/juce_RelativeCoordinatePositioner.h
@@ -45,6 +45,7 @@ public:
 
     void componentMovedOrResized (Component&, bool, bool);
     void componentParentHierarchyChanged (Component&);
+    void componentChildrenChanged (Component& component);
     void componentBeingDeleted (Component& component);
     void markersChanged (MarkerList*);
     void markerListBeingDeleted (MarkerList* markerList);
diff --git a/src/maths/juce_Expression.cpp b/src/maths/juce_Expression.cpp
index 738a62596a..a74b71ee25 100644
--- a/src/maths/juce_Expression.cpp
+++ b/src/maths/juce_Expression.cpp
@@ -337,7 +337,12 @@ public:
             visitor.useSymbol (Symbol (scope.getScopeUID(), getSymbol()->symbol));
 
             SymbolVisitingVisitor v (right, visitor, recursionDepth + 1);
-            scope.visitRelativeScope (getSymbol()->symbol, v);
+
+            try
+            {
+                scope.visitRelativeScope (getSymbol()->symbol, v);
+            }
+            catch (...) {}
         }
 
         void renameSymbol (const Symbol& oldSymbol, const String& newName, const Scope& scope, int recursionDepth)
@@ -346,7 +351,12 @@ public:
             getSymbol()->renameSymbol (oldSymbol, newName, scope, recursionDepth);
 
             SymbolRenamingVisitor visitor (right, oldSymbol, newName, recursionDepth + 1);
-            scope.visitRelativeScope (getSymbol()->symbol, visitor);
+
+            try
+            {
+                scope.visitRelativeScope (getSymbol()->symbol, visitor);
+            }
+            catch (...) {}
         }
 
     private:
@@ -1196,8 +1206,9 @@ double Expression::Scope::evaluateFunction (const String& functionName, const do
     throw Helpers::EvaluationError ("Unknown function: \"" + functionName + "\"");
 }
 
-void Expression::Scope::visitRelativeScope (const String&, Visitor&) const
+void Expression::Scope::visitRelativeScope (const String& scopeName, Visitor&) const
 {
+    throw Helpers::EvaluationError ("Unknown symbol: " + scopeName);
 }
 
 const String Expression::Scope::getScopeUID() const