Ok here's an idea. It worked for me today. When I load up NFS Most wanted, mine freezes when loading up. It would not log me on previous attempts. It tried to go through sign in, but had a box on screen after doing so saying sign in unsucessful.
Maybe sign in is the key before signing in when in game. On PS3 main screen before game locate PSN icon in list of icons. Sign in there!
Having done this I was able to play the game after starting up without it freezing on me!
Hope this helps you guy's gals who are freezing during multiplayer etc as mine only froze when loading the game itself. :-)
