Try doing what was said before: stick the cart, pull it off a little, and test. Rince and repeat, testing slightly different positions.
If you get no results, your port might be busted, or you got a bootleg cart.
I have this bootleg cart that won't run X-men vs Street Fighter unless I run either Pocket Fighter or Marver Super Heroes first, start a match, open the CD door and then boot XvSF.