I am having this problem too...it seems to be when I leave the computer on over night. When I come back to it in the morning it's all wacky and slow. The mouse jerks around and the GUI is choppy as hell. Iannxxx, what do you mean by "Have to run memory at exactly 400mhz"? Do you mean in BIOS settings or something? I've never messed with the timings before, so I'm pretty sure they're on 400 by default. On the other hand, I did have my FSB overclocked at the time I was noticing this problem, but I just turned it back to default. Do you think this could have been a cause too? I'm going to leave my system on again tonight, so we'll see what happens I guess...