this happend to my old ps2, all my dvd games had scratches( very light) but it ate my gt3 up, really bad, at first i thought i had knocked something over in my room, but it was my cd getting scratched!!!!! i took gt3 back and got a new one, also i got a new ps2 as i didnt want it to happen to any of my other games. it would make a noise and i could only start the game up if i went to browser and then pic the cd.
if you ring sony up they will replace it, but you may get a dodgy one ( like i did) but you will eventually get one that works, also if you tell them what happend to your game they give you a adress, you send the game there, they send you a new one back