Jim Thompson wrote:
I'm getting a crash that almost always is instigated while surfing a
graphically busy page (using Firefox), though other programs have
(rarely) caused it to fail.

It manifests itself as frozen raggedy looking video, OR a full POR
like you pressed the reset button.

What do you think... bad power supply or bad memory?

Thanks!

...Jim Thompson
Bad cooling on the processor chip and/or video card.
try SPEEDFAN (use google to get it), to show temperatures
inside.