It's not the game but a button stuck on your PSP. try to clean around it a bit using a small brush. If that doesn't help you may need to take the faceplate off to be able to get right at it There are three small screws (one on the bottom, two at the top) to remove for this.
If you are still under warranty, however, i would say contact Sony instead and ask them about repairs/ replacement. If you still have the receipt it's free of charge.