The game I run flickers heavily when I run stereo mode on the a 120Hz LCD screen.
Some games actually do natively not support 100hz or higher refresh rates. In some cases it is possible to force the game to use these refresh rates. Please check with the game developer if they support 100 to 120 Hz refresh rates.
If you are using a 120 Hz LCD make sure you have set the brightness to 100%.
Be aware that room light, especially flourescent lighting, can make you perceive a lot of flickering. Turn off lights if possible.