Display splinters, crashes w/ runtime error

I believe this problem originates with my nvidia drivers and software: I recently did some updating, uninstalling, and reinstalling of my GeForce 5200 driver via Device Manager, first trying to get a game to work and then trying to get my display back to normal. Windows says the card is working properly and most video displays properly, but when I log in to SL I get flickering, multicolor dogleg jags, though I can often see normal objects, terrain, and avatars where they're not obscured by the jags. After 2-10 minutes, I crash with a pop-up from Microsoft Visual C++ Runtime: Runtime Error, abnormal program termination. Setting all graphics preferences to minimum extends my time, but not by much, and SL is basically unusable except for quick communications and menu operations. Continued uninstalling/reinstalling of the driver has no effect.

Any recommendations? This is an XP system, Pentium 4 with GeForce 5200 128MB card and a competent but inexpert user.