Flicker in Shadow Warrior

[Ronald Railgun]

A friend gave me an old Aptiva with an AMD K-6 300 processor, and a Rage Pro Turbo APG 1x video card. I wanted to add it to the network and be able to play larger Shadow Warrior games.

Only problem is that there's a frequent and annoying flicker in 800x600 mode. It happens with any monitor, but does not happen at any other resolution. 640x480 isn't that bad. I could play that way, but I'd really like to fix this if possible.

Anybody got any idea what it could be? The video card works fine for everything else.