I think I may have a handle on what the problem is but want to run it by
some people to see if my logic is sound.

The machine is a dual-core Xeon running RH9 under the 2.4.20-20.9smp
kernel with an Nvidia 9520VS AGP card. Been running like a champ since
2004 until just this morning. I tend to leave the machine on all the
time, so it puts the monitor into power-saver mode after a bit. This
morning it would not come out of it and I had to reboot the machine to
get back in. Checked the logs, no errors anywhere, either in the
messages log or the XFree log.

Reboot goes perfect, work for a bit before having to go to the store.
Left myself logged in, screensaver kicked in. Got home, screensaver (the
GLPlanet one) is frozen. This time I had the sense to log in remotely
from another part of the home network. Machine is running fine, but the
X server process is pegged at 99% CPU. Tried to switch runmodes to
reinitialize X, but no dice. Tried to kill it manually, no dice. So I
reboot again.

On a hunch, after everything was up, I tried to start the game
"Chromium", which requires 2D acceleration. Boom, X server locks.
Reboot, tried some other stuff that uses 2D acceleration. A lock every time.

Turned the machine off and left it for a bit. Opened it, cleaned the
dust out, booted. Now 2D acceleration works perfectly again.

So could this be an overheat causing the issue? All the fans appear to
be running fine, including the one mounted on the GPU. I can live
without acceleration since I'm not a big gamer, but if it's starting to
overheat now, I wonder if it's just a matter of time before the whole
video card goes.

Thanks in advance for any advice.