Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I am using a mac pro. Apparently its pretty random when it comes to the intel machines. But it only happens on the intel ones.
 
Maybe this update for x11 that came out today will fix it.....downloading......:D
EDIT: no it did not fix it.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.