I worked around the problem by switching to the fglrx driver as mentioned in the comment above ( https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/273510/comments/12 ), so my main pain is gone.
If I can be of any help with tracking the bug in the radeon driver down on my particular hardware please drop me a line.
I worked around the problem by switching to the fglrx driver as mentioned in the comment above ( https:/ /bugs.launchpad .net/ubuntu/ +source/ xserver- xorg-video- ati/+bug/ 273510/ comments/ 12 ), so my main pain is gone.
If I can be of any help with tracking the bug in the radeon driver down on my particular hardware please drop me a line.