Two dead machines

I am having lots of problems.

1) My quad core Gateway PC running OpenSUSE 10.3 keeps rebooting every
hour or so. There is nothing in the logs that I can find. I ran
memtest86, and it has passed so far. Any suggestions?

2) My other dual Opteron machine running 10.3 (that dual boots to
Windows XP) will not start X, and so never gets to runlevel 5. That
seems to be the only error in /var/log/messages during startup. The X
server dies. I tried running sax2 as root. It cannot start its server,
and there is no /var/log/Sax2.log file.
I tried replacing xorg.conf with the default one, with no better
results.

Help please.

Thanks,
Jim
.