My non-LE 64MB 8500 started getting artifacts a while ago. Like strange planes popping up, FFXI had like rubber band like planar artifacts that stretched from my dude's belt off into infinity, etc.
I tried underclocking to no avail.
The card didn't used to do it - I got it used from a buddy and ran it for about 1-1.5 years before it started acting up.
A lot of googling on the internet (it was hard to find info) found some speculation about it being a power issue - some people had luck with a new PS. I knew mine wasn't power because nothing had changed (300W Antec PS).
I needed an upgrade anyway. Switched over to an MSI 9800pro refurbed for $170. Gave the 8500 to my wife. Still has the same symptoms. She can play Sims2 for about an hour before she starts to get artifacts.
Symptoms of the card:
Works fine in 2D. Works fine in 3D for a little while and then starts blipping out, or immediately has artifacts, depending on game/workload of the card. Depends on how tough the 3D is. UT2004 Demo looked fine, but C&C Generals was spazzing. Ditto for FFXI - worked fine for about an hour.
Quake 2 looked and played fine, though, even if I played hours of it
Solution: probable bad card. Get a refurbed 9800pro as a budget gaming card.
Good luck, though. If you get rid of them, tell me how, and I could save on buying the wife a new 3D card.