https://bugs.freedesktop.org/show_bug.cgi?id=30036
--- Comment #3 from Marek Olšák maraeo@gmail.com 2010-09-11 21:33:46 PDT --- Could you possibly test this kernel patch:
http://lists.freedesktop.org/archives/dri-devel/2010-September/003830.html
I am 99% sure it fixes this bug, but I haven't tested it myself.