After about an hour ubuntu starts to behave strangely:

A lot of resizing (vertically, but sometimes horizontally) redraws contents, but this is very annoying.
Is there a way to fix it?
Graphic card: 00:05.0 VGA compatible controller: nVidia Corporation C51 [GeForce Go 6100] (rev a2)
I'm using nvidia-current drivers (270.41.06-0ubuntu1).
