https://bugs.freedesktop.org/show_bug.cgi?id=39648
--- Comment #4 from almos aaalmosss@gmail.com 2011-07-29 10:36:49 PDT --- (In reply to comment #3)
The symptoms sound somewhat familiar. Can you try the patches from this thread: http://lists.x.org/archives/xorg-devel/2011-May/021908.html
I git cloned the xf86-video-ati repository, applied both patches from that ml-thread, replaced the radeon and ati driver modules of xorg with the compiled ones, and now everything seems to work correctly.