https://bugs.freedesktop.org/show_bug.cgi?id=44549
--- Comment #1 from Eric Bischoff ebischoff@nerim.net 2012-01-07 03:45:18 PST --- It's very similar to the problem described in http://lkml.indiana.edu/hypermail/linux/kernel/1105.2/03496.html
Nevertheless, it's not exactly the same hardware conditions, and the radeon driver patch that did solve that problem does not work for me.