Originally Posted by poltsy
Noticed the exact same thing on GTS 450 a while ago when debian started pushing xserver 1.11 in unstable. Going back to xserver 1.10 from backports made the issue disappear so I completely forgot about it.
same on 8600MGT the only thing that i changed was the x.org server when it started happening some year ago. if you use more than one monitor you might get the menu to open on a screen and the same coordinates of the opened menu get erased in the other monitor (you see the desktop wallpaper). I also get gnome widgets not rendering or windows showing behind rendering above. (even though they answer to commands too so logically they seems above even if from the look of it they seem behind).