Gateway EV910, flicker problem

Hi folks.

A Gateway EV910 is connected to a Hercules GTS Pro. With the 6.50 NVidia drivers everything is fine. With any higher release of driver, the monitor starts clicking on and off, like it's changing resolution but it's not, it does it in D3D and is OK at the desktop, unless I play a windows game and then it does it from release 7.52 onwards.

I've tried changing the resolution, optimal resolution over manual settings, tweaking D3D settings but to no avail. Even Hercules own driver causes the problem.

Any help or advice, very gratefully received.

PS Running win98 SE.