It would be nice if you could try Ubuntu 8.04 LTS development version's live CD and see if this problem is finally fixed. For example the current one is at: http://cdimage.ubuntu.com/ports/daily-live/20080310/hardy-desktop-powerpc.iso
The link will be gone in a few days, after that the latest one can be found in subdirectories of http://cdimage.ubuntu.com/ports/daily-live/
Ubuntu 8.04 has a new 6.8.0 version of xserver-xorg-video-ati, which has a very large number of bug fixes etc.
It would be nice if you could try Ubuntu 8.04 LTS development version's live CD and see if this problem is finally fixed. For example the current one is at: http:// cdimage. ubuntu. com/ports/ daily-live/ 20080310/ hardy-desktop- powerpc. iso
The link will be gone in a few days, after that the latest one can be found in subdirectories of http:// cdimage. ubuntu. com/ports/ daily-live/
Ubuntu 8.04 has a new 6.8.0 version of xserver- xorg-video- ati, which has a very large number of bug fixes etc.