the videocard drivers to the latest version. If that doesn't help, see if changing the hardware accelleration in the display properties helps.
I have Windows XP Media Center and and ATI Radeon HD 2600 pro vid card. During any type of game play, i.e. COD or Quake, if I adjust the volume or use the Q3E minimizer, I have to exit the game and readjust the brightness in the game system settings before I can play again because the screen gets dark. Other friends I play with do not have this problem, so I hope someone knows how to fix this.