Comment 39 for bug 38131

Turns out this was/is a problem with a new version of xserver-xorg-video-intel.
The problem disappears when using vesa driver or downgrading to an older version of xserver-xorg-video-intel.

For anyone interested: I have an Intel X3100 (GM965) and
xserver-xorg-video-intel Version 2:2.2.0-1 does not work (problem description see post above)
xserver-xorg-video-intel Version 2:2.1.1-4 does work