I have also had lock-ups from time to time. The non-hard lock-up I get is with Netscape...sometimes it runs out of control and hogs CPU and freezes up. I can kill it, so not too big a deal. At times I'll get a hard lock-up and forced re-boot. I think these events may be related (ie. I'm having the Netscape problem at the same time as I'm doing something else on the desktop and the hard lock-up occurs -- this is conjecture).
It seems that the Netscape freezes are Java related. Any takers on this one? Cheers, Paul