diff --git a/debug/org.eclipse.cdt.debug.core/ChangeLog b/debug/org.eclipse.cdt.debug.core/ChangeLog
index 35887993214..4775a97997f 100644
--- a/debug/org.eclipse.cdt.debug.core/ChangeLog
+++ b/debug/org.eclipse.cdt.debug.core/ChangeLog
@@ -1,3 +1,9 @@
+2004-11-18 Mikhail Khodjaiants
+	Worker threads can try to evaluate expressions on the stack frames that 
+	have already been disposed. A flag is added to identify that the stack 
+	frame is disposed.
+	* CStackFrame.java
+
 2004-11-19 Alain Magloire
 
 	Clear the confusion about sublist of stackframes.
diff --git a/debug/org.eclipse.cdt.debug.core/src/org/eclipse/cdt/debug/internal/core/model/CStackFrame.java b/debug/org.eclipse.cdt.debug.core/src/org/eclipse/cdt/debug/internal/core/model/CStackFrame.java
index 8d6690edd4d..2e06c1315a9 100644
--- a/debug/org.eclipse.cdt.debug.core/src/org/eclipse/cdt/debug/internal/core/model/CStackFrame.java
+++ b/debug/org.eclipse.cdt.debug.core/src/org/eclipse/cdt/debug/internal/core/model/CStackFrame.java
@@ -79,6 +79,11 @@ public class CStackFrame extends CDebugElement implements ICStackFrame, IRestart
 	 */
 	private List fExpressions;
 
+	/**
+	 * Need this flag to prevent evaluations on disposed frames. 
+	 */
+	private boolean fIsDisposed = false;
+
 	/**
 	 * Constructor for CStackFrame.
 	 */
@@ -477,6 +482,7 @@ public class CStackFrame extends CDebugElement implements ICStackFrame, IRestart
 	}
 
 	protected void dispose() {
+		setDisposed( true );
 		getCDISession().getEventManager().removeEventListener( this );
 		disposeAllVariables();
 		disposeExpressions();
@@ -661,9 +667,11 @@ public class CStackFrame extends CDebugElement implements ICStackFrame, IRestart
 	 * @see org.eclipse.cdt.debug.core.model.ICStackFrame#evaluateExpression(java.lang.String)
 	 */
 	public IValue evaluateExpression( String expressionText ) throws DebugException {
-		CExpression expression = getExpression( expressionText );
-		if ( expression != null ) {
-			return expression.getValue( this );
+		if ( !isDisposed() ) {
+			CExpression expression = getExpression( expressionText );
+			if ( expression != null ) {
+				return expression.getValue( this );
+			}
 		}
 		return null;
 	}
@@ -718,7 +726,10 @@ public class CStackFrame extends CDebugElement implements ICStackFrame, IRestart
 		}
 	}
 
-	private CExpression getExpression( String expressionText ) throws DebugException {
+	private synchronized CExpression getExpression( String expressionText ) throws DebugException {
+		if ( isDisposed() ) {
+			return null;
+		}
 		if ( fExpressions == null ) {
 			fExpressions = new ArrayList( 5 );
 		}
@@ -740,4 +751,12 @@ public class CStackFrame extends CDebugElement implements ICStackFrame, IRestart
 		}
 		return expression;
 	}
+
+	protected boolean isDisposed() {
+		return fIsDisposed;
+	}
+
+	private synchronized void setDisposed( boolean isDisposed ) {
+		fIsDisposed = isDisposed;
+	}
 }
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