Computer freezing. Probably related to my new motherboard.

My motherboard passed away in a most untimely manner at just over a year of age on Christmas morning. (Right after I'd finished installing my shiny new Skyrim, heh) I've since replaced the faulty board and gotten it working again, and even played my first few hours of Skyrim.

But twice today I've had my computer freeze on me. Everything just stops: none of my input works, audio output stops, and the screen freezes. No blue screen to help diagnose it; I have to press the reset button. Presumably this has to do with my new motherboard, maybe some driver issue I haven't worked out yet. Obviously an issue with such sporadic, seemingly random behavior is hard to troubleshoot. Does anyone here have any idea of things I could try to fix it? Possible culprits? Thanks!