Also make sure you are running the game on administrator, and that if you have a Anti-virus program check so that it doesn't block the game.
Have you downloaded any new maps or such?
Try what Bloo told you to do - change the rendering system between OpenGL and Direct3D9 and see if it works after that.
Good luck!
Cheers~ // Shallow
(Pops in :3) If Feareh suggestion don't work, try using 'Character Reset' It helps me when I get this error. So I think you should try it. :)
(http://i48BannedImageSite/29m88ld.jpg)
Good luck