Dependency Diagram not responding to edit events

1) Open Dependency Diagram for a virtual table
2) Delete the Virtual table
3) Diagram does nothing and still shows deleted table
4) Refresh Diagram and it turns white due to exception:

java.lang.IllegalArgumentException: TransformationHelper.getTransformationMappingRoot:null or invalid target.
at com.metamatrix.modeler.internal.transformation.util.TransformationHelper.getTransformationMappingRoot(TransformationHelper.java:2493)
at com.metamatrix.modeler.internal.transformation.util.TransformationHelper.getTransformationMappingRoot(TransformationHelper.java:2534)
at com.metamatrix.modeler.transformation.ui.model.TransformationDiagramModelFactory.getTransformationObject(TransformationDiagramModelFactory.java:356)
at com.metamatrix.modeler.transformation.ui.model.TransformationDiagramModelFactory.getTransformationDiagramContents(TransformationDiagramModelFactory.java:151)
at com.metamatrix.modeler.transformation.ui.model.TransformationDiagramModelFactory.createModel(TransformationDiagramModelFactory.java:107)
at com.metamatrix.modeler.diagram.ui.editor.DiagramEditor.createModel(DiagramEditor.java:391)
at com.metamatrix.modeler.diagram.ui.editor.DiagramEditor.setDiagram(DiagramEditor.java:1484)
at com.metamatrix.modeler.diagram.ui.editor.DiagramEditor$5.run(DiagramEditor.java:1180)
at com.metamatrix.ui.internal.viewsupport.UiBusyIndicator.showWhile(UiBusyIndicator.java:80)
at com.metamatrix.modeler.diagram.ui.editor.DiagramEditor.openContext(DiagramEditor.java:1178)
at com.metamatrix.modeler.diagram.ui.actions.RefreshAction.doRun(RefreshAction.java:50)