OpenGL used to run on G-200.....doesn't on TNT2M64....HELP

I just installed a Riva TNT2 M64 32Mb card.
I used to have no major problems running Open GL games on my old G-200 card.
Now, OpenGL games crash with a message saying" Can’t set pixel format" and sometimes also “Vendor string is NULL”
Help please! Don’t want to go back to the G-200

By the way, i tried both the drivers that came with the board and Detonator 3 drivers.
Tried using GL setup too, and still nothing.
D3D seems to work fine though

[This message has been edited by DoctorFun (edited 01-04-2001).]

OK, I got it runing now. Used the ;DVA trick I read in another thread. But now I have a new problem:
I’m playing FAKK2 and the textures turn into lots of colourful squares. Everytime I start the game over, it seems worse.
I tried fiddling with the graphics controls, desktop color depth, etc…and nothing.
Oh, most of the times the loading screens get garbled with random colour dots.
Can anyone help please?