Hi,

I guess DoEvents won't cause a crash if there aren't any messages in the flowchart window message queue . So one time it might work, and the next time not ...

Try the following:

- set EventFlags(fFireMouseUpAfterModfProcessing) = true; That will make the MouseUp event raised after the control finishes processing the selection change.

- in SelectionChanged only set some boolean flag = true

- in MouseUp, if that flag is set, execute the code that is currently called from SelectionChanged. Now it should be safe to call DoEvents, because the control is already at the end of its WM_BUTTONUP handler.

Stoyan