OpenGL causes hard system lockups

[Matthew Garman <garman@c1858677-a.chmpgn1.il.home.com>]

I bought a Matrox Millenium g450 over the summer.  I got it setup to do
hardware accelerated 3d with XFree 4.x.

The only real 3d apps I've used are the "glxgears" test program, and the
3d screensavers that can be built with the xscreensaver package.

Some of these 3D screensavers will unexpectedly lock up my system---and I
mean *completely* lock up my system, can't ctrl-alt-f[1-6] to switch to a
text console, I can't kill X with ctrl-alt-backspace, etc.  Nothing works.

Obviously I don't like lockups like that, since I have to restart my
computer without shutting down properly.

Anyone know what might be causing this?  Is it likely a hardware problem?
Anyone had any experience with this kind of thing?

Thanks!
Matt

-- 
Matt Garman, garman@uiuc.edu
"I'll tip my hat to the new constitution, Take a bow for the new revolution
 Smile and grin at the change all around, Pick up my guitar and play
 Just like yesterday, Then I'll get on my knees and pray..."
            -- Pete Townshend/The Who, "Won't Get Fooled Again"