Gran Turismo 5 (GT5) won't play on my PS3?

OK. I bought a PS3 for my husband for his birthday and GT5. We put the disc in and it played just fine for a few minutes, then the game froze. So, we reset the PS3 and put the game back in. The system reads GT5 and will play the beginning credits, but when we get to the "Warning" screen, it freezes. So, we took back the GT5 game and got a new one. This one does the exact same thing - freezing after a few credits. I can't imagine we would get two discs in a row that don't work so it makes me wonder if it is the system. We have played two other games on it just fine - no problems. HELP please! GT5 is the reason we bought the PS3!