So I'm a Mac user going back to the Mac Plus, LC, IIci, etc. I just bought a 27" iMac i7 and upgraded it to 12gb and manually moved over my documents/application/etc files carefully as I was moving from a very old Powermac dual G5. The machine is PERFECTLY stable when I sit at it...In fact I've used it for several hours in a row with no issue. HOWEVER, when I walk away and come back it won't wake up! It SEEMS to still be running as it is very warm, but it won't let me wake it back up. Mouse, nothing. Keyboard, nothing. Power button, nothing! I MUST force a reboot! Memory seems to test fine with Memtest 4.22 and Cocktail has been run. WTF?!? Ideas?