Comment 2 for bug 560571

This is a fglrx bug, kas_spin_lock and KAS_GetExecutionLevel are totally not preempt safe. Unfortunately this is most likely hurting your GPU performance and you would be better off using the -generic kernel. I see you are on a laptop as well, and the preempt kernel very negatively impacts your battery life if that is an issue so that's could be another reason to use the standard kernel.