G2D, have you tried a DVD cleaner as mine wasn'r reading certain discs, PGR3 generally, but not had a problem so probably just some dust on the laser.
I made a concious decision not to get GTA IV as I didn't want ot miss any decent biking weather playing games. I almost broke and pre-ordered in Game but they weren't let any more people pre-order. Great, saved me ?40. Until this afternoon, bored at work, bought it off ebay. Idiot.
So looking forward to it