X800 Graphics card and Crashing issues?

Hi, I have a strange issue with Second Life. Sometimes, for no apparent reason, I'd be panning around something I made, or in a high-prim area, and the screen will freeze for about a second, my monitor will turn black, and my computer will beep as it restarts. Sometimes it can recover, and Second Life just ends up crashing, but it really frustrates me when I'm scripting, or trying to carry out a conversation and my computer is all of the sudden restarting. My graphics card is good, It can handle everything at top notch (except draw distane) and give me at least 20-30 fps. I've tried playing with the settings, I've upgraded to the latest Catalyst drivers, and it still happens. My question is if this is a graphics card issue, or is it my processor? AMD 3200+ ~2.0 ghz. Nothing is overclocked, nothing is running in the background. Is there anyone else having this happen to them?

I have the X1300 512mb AGP card and the Catalyst drivers seemed to cause all kinds of havok for me here and many other places as well. I downloaded the Omega drivers instead. jsut make sure to completely uninstall every bit of software relating to ATI, then restart and install the Omega drivers

http://www.omegadrivers.net/