I've been having endless trouble with my new pc, crashing with no warning and immediately rebooting without an indication of the cause. It has the most trouble playing .bink videos for opening credits on CoD4 and UT 3, which makes it crash almost instantly. When I remove the movie folders for the offending games, they will load into the game, but after 10-30 minutes of play pretty much everything invariably ends in the game crashing with the same reboot. CoH-OF will play the intro videos, but also crashes with a reboot after about the same amount of time.
I've found that the .bink videos will play, and I only get in game crashing, if I use the display drivers that came with the GPU (version 7.8 catalyst drivers I believe), but with them up to date videos and in game crash like mentioned.
I bought the 2nd GPU (the ASUS one) thinking it was the sapphire card causing the problem, but on its own or in crossfire with the sapphire, the ASUS card still has the same crashing. I'm not sure what the suspect part is now. I've tried formatting, and even with just the display drivers and a patched copy of the offending games, it still crashes in all the same ways.