"Fatal error" crash message

When I start the game and I go to start a match (skrimish vs AI, & campain) the game keeps crashing on me and giving me a "fatal error" message then I'm sent back to the main menu. The message reads "An internal error has been encountered and the game is unable to continure normally. Please notify the mod's creators about this issue, or visit our website at (this website). The cause of this error could not be determined." How do I fix it?