https://bugs.freedesktop.org/show_bug.cgi?id=36934
--- Comment #15 from almos aaalmosss@gmail.com 2011-10-22 07:00:31 PDT --- Since I upgraded to mesa 7.11 I experience significantly less corruption than with 7.10. It still happens sometimes, though. Now I removed the virtualbox modules to give it a try.
Meanwhile, I also tried to reproduce the firefox image corruption in a vnc screen, and it didn't happen, while running firefox normally is still bad. I think it means this is not a bug in firefox, but in xorg/mesa/libdrm/linux somewhere.