I have an app based on the model-viewer winforms sample.  Every once in a while (but often enough to be annoying), the GraphicsDevice-based window stops painting.  It doesn't seem to be triggered by anything special (e.g. minimizing the window does not trigger it).

It's still getting paint messages (my Draw code is being executed), but nothing shows up.  Resizing the window 'vigorously' fixes it.

I looked at the GraphicsDevice object in the debugger when it is reproing, and it seemed fine.

Any ideas on what I can do to track this down?