If the game screen flashes off and on, flickers, or characters appear and flicker in front of the game screen, it means the currently installed video card driver may not fully support DirectX.
Press the Alt and Tab keys together (Alt + Tab) several times. This toggles the game screen on and off. Doing this may minimize or eliminate the problem.
If the problem continues, try updating your video driver. For information on how to do this, check our Graphics Problems help page.