XP or Vista?
You could try turning V-Sync ON,if you haven't already.
Enable vsync by hitting the tilde key (~) ,then in the consol window type 'preferences' and hit enter.
You'll find the option to turn on/off vsync and many other settings.
If Vista have you tried it in compatibility mode for xp or from xp to compatibility for Windows 98.
Have you applied the latest game patch?
As a bit of an awkward work around,you could try turning your monitor brightness right up before you play the game if nothing works.