If no one here knows what's going on then I'd suggest taking the game to a store and have them try it out to see if it's the disk or your console. If it's the disk then bitch up a storm with whoever sold it to you. If it's the console then take it to a store and have them try it.
By the way, which PS3 do you have? 20GB, 40GB, 60GB or 80GB?
If you're PS3 is hooked up to the internet then it should prompt you to update. If you're not then you'd have to find the download on the official PlayStation 3 website.