seems like i have similar problem.
My system doesn't run stable enough about 140 FSB, 1.55 Vcore, everything else default. It could be the USB intellimouse. But having USB is so much more convenient!
P4 1.6a (5/22/02), stock hsf, Asus P4B 533 w/audio, 2x256 MB Samsung PC2700, bios rev 1004, XP...