You don't say what console. Is it just this game or others as well? Check the fan at the back of the console is running. Consoles overheat after a while and usually crash or lock up part way through a game (usually when you are at a critical point in the game). Check the disk for marks or scratches as they can show different problems with different games. Finally, it could be a dirty laser which sometimes may be fixed with a laser cleaning CD.
Dave
March 2006