Comment 12 for bug 665546

Got the same problem here. Some additional information:
Also occurs with Metacity when Compositing (gconf: apps/metacity) is enabled, so I filed a bug against the nvidia drivers that got marked duplicate. Can anyone confirm that this is not just a compiz problem? If so, we should figure out where exactly the problem lies...

Seeing that people with different drivers (and different WMs) got this problem, my best guess would be the X.org Compositing Extension. Anyone with a way to prove that?