Comment 52 for bug 351990

jpkx1984, you can try 2.6.28-12.43 as jtholmes suggests here:
https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/348332/comments/35
For me 2.6.29.2 is working. It has been more than 1 day and no freeze. If I have one I will post a message here.