diff --git a/dsf-gdb/org.eclipse.cdt.dsf.gdb.multicorevisualizer.ui/src/org/eclipse/cdt/dsf/gdb/multicorevisualizer/internal/ui/view/MulticoreVisualizer.java b/dsf-gdb/org.eclipse.cdt.dsf.gdb.multicorevisualizer.ui/src/org/eclipse/cdt/dsf/gdb/multicorevisualizer/internal/ui/view/MulticoreVisualizer.java
index f3f7ac3e792..f9ea96ac601 100755
--- a/dsf-gdb/org.eclipse.cdt.dsf.gdb.multicorevisualizer.ui/src/org/eclipse/cdt/dsf/gdb/multicorevisualizer/internal/ui/view/MulticoreVisualizer.java
+++ b/dsf-gdb/org.eclipse.cdt.dsf.gdb.multicorevisualizer.ui/src/org/eclipse/cdt/dsf/gdb/multicorevisualizer/internal/ui/view/MulticoreVisualizer.java
@@ -8,6 +8,7 @@
  * Contributors:
  *     William R. Swanson (Tilera Corporation) - initial API and implementation
  *     IBM Corporation
+ *     Marc Dumais (Ericsson) - Bug 399281
  *******************************************************************************/
 
 package org.eclipse.cdt.dsf.gdb.multicorevisualizer.internal.ui.view;
@@ -705,10 +706,11 @@ public class MulticoreVisualizer extends GraphicCanvasVisualizer
 	protected void setCanvasModel(VisualizerModel model) {
 		final VisualizerModel model_f = model;
 		GUIUtils.exec(new Runnable() { @Override public void run() {
-			m_canvas.setModel(model_f);
-			
-			// Update the canvas's selection from the current workbench selection.
-			updateCanvasSelectionInternal();
+			if(m_canvas != null) {
+				m_canvas.setModel(model_f);
+				// Update the canvas's selection from the current workbench selection.
+				updateCanvasSelectionInternal();
+			}
 		}});
 	}
 	
diff --git a/dsf-gdb/org.eclipse.cdt.dsf.gdb.multicorevisualizer.ui/src/org/eclipse/cdt/dsf/gdb/multicorevisualizer/internal/ui/view/MulticoreVisualizerCanvas.java b/dsf-gdb/org.eclipse.cdt.dsf.gdb.multicorevisualizer.ui/src/org/eclipse/cdt/dsf/gdb/multicorevisualizer/internal/ui/view/MulticoreVisualizerCanvas.java
index 291a5a95a8d..093501c1cb4 100755
--- a/dsf-gdb/org.eclipse.cdt.dsf.gdb.multicorevisualizer.ui/src/org/eclipse/cdt/dsf/gdb/multicorevisualizer/internal/ui/view/MulticoreVisualizerCanvas.java
+++ b/dsf-gdb/org.eclipse.cdt.dsf.gdb.multicorevisualizer.ui/src/org/eclipse/cdt/dsf/gdb/multicorevisualizer/internal/ui/view/MulticoreVisualizerCanvas.java
@@ -11,6 +11,7 @@
  *     Marc Dumais (Ericsson) - Bug 396184
  *     Marc Dumais (Ericsson) - Bug 396200
  *     Marc Dumais (Ericsson) - Bug 396293
+ *     Marc Dumais (Ericsson) - Bug 399281
  *******************************************************************************/
 
 package org.eclipse.cdt.dsf.gdb.multicorevisualizer.internal.ui.view;
@@ -303,7 +304,9 @@ public class MulticoreVisualizerCanvas extends GraphicCanvas
 	 */
 	public void requestUpdate() {
 		GUIUtils.exec(new Runnable() { @Override public void run() {
-			m_updateTimer.start();
+			if (m_updateTimer != null) {
+				m_updateTimer.start();
+			}
 		}});
 	}
 	
@@ -867,7 +870,9 @@ public class MulticoreVisualizerCanvas extends GraphicCanvas
 	/** Removes external listener for selection change events. */
 	@Override
 	public void removeSelectionChangedListener(ISelectionChangedListener listener) {
-		m_selectionManager.removeSelectionChangedListener(listener);
+		if (m_selectionManager != null) {
+			m_selectionManager.removeSelectionChangedListener(listener);
+		}
 	}
 	
 	/** Raises selection changed event. */
diff --git a/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/VisualizerViewer.java b/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/VisualizerViewer.java
index a9c71c2d1b3..344e3cddf94 100644
--- a/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/VisualizerViewer.java
+++ b/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/VisualizerViewer.java
@@ -7,6 +7,7 @@
  *
  * Contributors:
  *     William R. Swanson (Tilera Corporation)
+ *     Marc Dumais (Ericsson) - Bug 399281
  *******************************************************************************/
 
 package org.eclipse.cdt.visualizer.ui;
@@ -29,6 +30,8 @@ import org.eclipse.jface.viewers.ISelectionChangedListener;
 import org.eclipse.jface.viewers.ISelectionProvider;
 import org.eclipse.jface.viewers.SelectionChangedEvent;
 import org.eclipse.swt.SWT;
+import org.eclipse.swt.events.DisposeEvent;
+import org.eclipse.swt.events.DisposeListener;
 import org.eclipse.swt.events.MenuDetectEvent;
 import org.eclipse.swt.events.MenuDetectListener;
 import org.eclipse.swt.events.PaintEvent;
@@ -97,6 +100,13 @@ public class VisualizerViewer extends PageBook
 	public VisualizerViewer(VisualizerView view, Composite parent) {
 		super(parent, SWT.NONE);
 		initVisualizerViewer(view, parent);
+		// so we're notified when the widget is disposed
+        addDisposeListener(new DisposeListener() {
+            @Override
+            public void widgetDisposed(DisposeEvent e) {
+                dispose();
+            }
+        });
 	}
 	
 	/** Dispose method. */
@@ -431,7 +441,9 @@ public class VisualizerViewer extends PageBook
 
 	/** Removes external listener for selection change events. */
 	public void removeSelectionChangedListener(ISelectionChangedListener listener) {
-		m_selectionManager.removeSelectionChangedListener(listener);
+		if(m_selectionManager != null) {
+			m_selectionManager.removeSelectionChangedListener(listener);
+		}
 	}
 	
 	/** Raises selection changed event. */
diff --git a/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/canvas/BufferedCanvas.java b/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/canvas/BufferedCanvas.java
index b4f2778cef4..e2112ab95fd 100755
--- a/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/canvas/BufferedCanvas.java
+++ b/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/canvas/BufferedCanvas.java
@@ -7,6 +7,7 @@
  *
  * Contributors:
  *     William R. Swanson (Tilera Corporation)
+ *     Marc Dumais (Ericsson) - Bug 399281
  *******************************************************************************/
 
 package org.eclipse.cdt.visualizer.ui.canvas;
@@ -68,8 +69,10 @@ public class BufferedCanvas extends Canvas
 	
 	/** Cleans up control. */
 	protected void cleanupBufferedCanvas() {
-		removePaintListener(this);
-		removeControlListener(this);
+		if(!this.isDisposed()) {
+			removePaintListener(this);
+			removeControlListener(this);
+		}
 		if (m_doubleBuffer != null) {
 			m_doubleBuffer.dispose();
 			m_doubleBuffer = null;