Yesterday when using my 15" Macbook Pro under a heavy load (watching a HD movie + several background tasks) the display froze on a still image, couldn't forse quit, so had to hold down power button to restart. Now when I use it, it does the same a random intervals. So far I've tried; Formatting the HD and reinstalling the OS. Booting from the CD and doing a HD repair/check. It comes up OK. I've tried to do a hardware test (holding "D" on the install disk), but it always freezes before it can fully boot. Booted with just the 2GB stick of RAM installed, then wit just the 4GB stick to see if I had bad RAM. I'm thinking that it's either a problem with the logic board or the RAM. Thinking it's not the RAM or I wouldn't be able to run it for any time. Any ideas what I should do next? I'm tempted to try another HD in it just so I can rule it out.