I'm having alot of trouble aswell, the GT5P first loading screen (with the flashing LOADING) simply gets stuck and never stops loading. I don't get this problem when the ethernet cable is not connected though, so now when I load GT5P without the cable, then connect the cable and try to access any online content, the game just freezes. Right now, I've left the loading screen on for about an hour to no success. So now I'm stuck with offline playing which is frankly kinda boring, or nothing. So far I've already gone through 3 PS3's which haven't gone well, and I'm simply sick of this now. I feel like getting rid of the PS3 idea altogether. I hope this problem solves itself in the next few days, or I might just consider getting rid of the PS3 for good.
I really hope the problem is GT5, not the PS3.