Sometimes when i join the server i cant see anything just a simple one colored screen. When moving with mouse the color changes to blue (probably looking towards the sky) or different colors (Green/Brown/Grey probably when looking into a building or ground). When i press ESC to bring up the menu and select exit it opens up the Main Menu with the same one colored background (witch same simple colors). Only thing that works is to close the game completely and start it again.
Other games runs perfectly fine. I own a GeForce 260 GTX.