Game freezing after defeating #1 on the Blacklist, Razor

Game freezing after defeating #1 on the Blacklist, Razor

I own Need for Speed: Most Wanted for XBox 360. I made it all the way through the game to Blacklist #1,Razor. I completed all of Razor's required races, milestones, and bounty, and then I challenged Razor. I beat all of his races, but at the end of the last race against Razor, at the point when you cross the finish line, after a snapshot of your car is taken, I pressed the A button to continue, and suddenly, my game froze up. The XBox Guide Button wasn't working, and neither were any of the other buttons. I waited about five minutes too see if anything would happen, but nothing did. I had to shut off my system and turn it back on. Of course, my progress of beating Razor wasn't saved, and I now have to challenge him all over again.Can anyone help me determine the problem, or help me find a solution? This game has frozen on me before, and I think that a majority of the times it has froze up, they were NOT random ocurrences. I bought this game used, and the case and manual were in poor condition, though the disc appeared fine, and still, even now I can't see any scratches on the disc. But, the game has frozen only at specific times. For example, if I go into My Cars from the main menu, and then into Career Mode, the game will freeze.This has happened almost every time I do this. The game also froze after I defeated #2 on the Blacklist, Bull, after I had selected the third mystery Reward Marker. I reset my system and beat Bull again. I chose the third marker again, and the game froze. I defeated Bull a third time, and chose the first and second mystery Reward Markers instead of the third one, and the game DIDN'T freeze. It turned out that the third marker was Bull's Pink Slip.For additional information: I defeated Razor with a fully upgraded Lamborghini Murcielago. I didn't try defeating Razor again, because being that I have had problems exactly like this before, and the game froze right after I won the last race, most likely the game will just freeze up again. Also, I am new to this website, so I really don't know much about it. I apologize for having such a lengthy explanation and question, but I wanted to make the question as clear as possible. Your help is GREATLY appreciated, and I will accept whatever you think. Anyone that thinks that they can help me, please respond back.