Marking as confirmed, because I have the feeling it is a duplicate of bug #16873. I did asked there someone to confirm.
** Changed in: xserver-xorg-video-ati (Ubuntu) Status: Unconfirmed => Confirmed -- r100 lockups during/after dri https://launchpad.net/bugs/15219 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs