Open GL Flicker on External Display

I have a 700 mhx PIII w/128mb ram, and a 32mb ATI Rage Mobility M4. open gl games like Q2, Q3A, and Star Trek Voyager Elite force run just fine on the built in LCD Panel on my laptop, but when i use the s-video out to connect to a sony tv, i have problems with the screen flickering during gameplay. D3d games and games based on the unreal engine seem to run fine, but any game based on the q2 or q3 engine has this problem… any suggestions on how to correct it?