RB error: CategoryTreeModel dnu

Using D4 & the RB port for it, I occassionally get the following
walkback. Usually when I'm changing buffers. I can never get out of it.
Luckily, I can usually go save my packages and then kill the image and
restart.

Anyone else see this?

Eric


2:10:15 PM, Friday, November 09, 2001: Unhandled exception - a
MessageNotUnderstood('CategoryTreeModel does not understand #at:ifAbsent:')

CategoryTreeModel(Object)>>doesNotUnderstand:
MultipleSelectionListView(IconicListAbstract)>>objectFromHandle:ifAbsent:
MultipleSelectionListView(ListView)>>onDisplayDetailsRequired:
MultipleSelectionListView(IconicListAbstract)>>nmGetDispInfo:
MultipleSelectionListView(ListView)>>nmNotify:
CardContainer(View)>>wmNotify:wParam:lParam:
CardContainer(View)>>dispatchMessage:wParam:lParam:
[] in InputState>>wndProc:message:wParam:lParam:cookie:
BlockClosure>>ifCurtailed:
ProcessorScheduler>>callback:evaluate:
InputState>>wndProc:message:wParam:lParam:cookie:
MultipleSelectionListView(ControlView)>>defaultWindowProcessing:wParam:lParam:
MultipleSelectionListView(ControlView)>>wmPaint:wParam:lParam:
MultipleSelectionListView(View)>>dispatchMessage:wParam:lParam:
[] in InputState>>wndProc:message:wParam:lParam:cookie:
BlockClosure>>ifCurtailed:
ProcessorScheduler>>callback:evaluate:
InputState>>wndProc:message:wParam:lParam:cookie:
InputState>>pumpMessage:
InputState>>loopWhile: