You'd be surprised.
I believe you have seen quite the variety by now :-)
Is desktop-effects or compositing enabled?
Neither. In fact, my xorg.conf says
Section "ServerFlags"
Option "AIGLX" "off"
EndSection
Section "Extensions"
Option "Composite" "Disable"
EndSection
Have you tried reproducing without nvidia driver and/or using vesa
driver?
Fair enough question. I now switched to "nv". I should have an answer in
half an hour or so - the problem never takes longer to appear.
Thank you
Hans