Need help, opengl games making my screen flicker black

I’m running windows 7 x64, Nvidia GeForce go 7900gs
Every time I try to play games that use Opengl, I have the issue of black bars flickering up and down
This occurs with Wolf:ET, quake 3, red eclipse etc
Scratching my head, have tweaked everything in game and in the Nvidia control panel, I’ve changed refresh rate and everything
Any help would be greatly appreciated