One of my friends had this problem a while ago, he was using some TNT-based video card too.
He fixed the problem by turning GL Extensions OFF in the "video" menu.
I think you're talking about the problem where your regular textures are moslt yreplaced by flickering black texture thingies... it's a hard thing to describe, I know.
Also, this might not help, but it will in the long run, make sure you have the latest version of DirectX, which should be 9.0c.
Glad to help, and I wish I could get paid doing it.