After deinstalling xserver-xorg-video-nouveau everything works as expected. So it seems to be a problem of the interaction of the driver with the graphics card:
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation NV31 [GeForce FX 5600] [10de:0312] (rev a1) (prog-if 00 [VGA controller])
I changed the target of this bug accrodingly.
Since it's a friend's computer, I won't be able to do more testing on this.
After deinstalling xserver- xorg-video- nouveau everything works as expected. So it seems to be a problem of the interaction of the driver with the graphics card:
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation NV31 [GeForce FX 5600] [10de:0312] (rev a1) (prog-if 00 [VGA controller])
I changed the target of this bug accrodingly.
Since it's a friend's computer, I won't be able to do more testing on this.