https://bugs.freedesktop.org/show_bug.cgi?id=55006
--- Comment #4 from spamfang1199@yahoo.de 2012-09-18 17:06:14 UTC --- Firmware linux-free & non-free are installed.
I tested Linux 3.2 again, this time with radeon.agpmode=-1. It seems to work for me. I put the machine under heavy load and played several vids at the same time: no freeze so far.
So what do you guess the problem is? And in case you solve the bug, could you backport it to Linux 3.2 too?