This may be caused by a bad game disc, or problems with your PlayStation console.
  • Make sure your disc is not scratched or dirty.
  • Make sure your PlayStation is in a cool, well ventilated space.
  • Try deleting the game data on your console. This should not affect your game save since that is saved in a different folder.
  • Try the game on another PlayStation. If the same problem happens on another PlayStation, then it is most likely the game disc is broken. 
If the steps above do not fix the problem, then the problem maybe with your PlayStation and you will need to contact Sony Consumer/Technical support at http://us.playstation.com/support/index.htm

NOTE: Activision cannot guarantee 3rd party hardware on PlayStation systems will completely work (including, but not exclusive to: Memory Cards, controllers, chips, and cables). If you have ruled out any problems with your PlayStation, and have decided that you need a disc replacement, please go to Warranty & Returns.