Aye, as Oddguy said give your disc a clean, and try again. If theres no scratches/doesn't fix, then its an unfortunate problem :\ (If you don't want to buy a new game, just do the skip segment cheat. Just look on gamefaqs.com.(if you don't mind missing out a small chunk of VicePresident Aslik's stuff). < /end cheating>
Hope this helped at all!
