PS3 lock up

Has anyone had their PS3 lock up on them?

I was playing on sunday for a couple of hours is it locked up 2x. I finally shut it down, got tired of having to go back are start over. Was play COD4

thanks

I've had a few lock ups, and some other weird issues with the PS3. The other night, the screen would just go black when inserting a PS2 disc or DVD. I had to power cycle it each time. I popped in a PS3 game, it came up fine, and then the DVDs and PS2 games would load just fine again.

was not playing online, it was a little hot though. didnt know if that is a known problem.