i found a way to load the save files after a freeze after som research. if you log out from Playstation Network and then start the game u should be able to run the save file. At least it worked for me. But still don't have any sulution for the freeze problem.
Btw, after you loaded the save file u should be able to log on Playstation Netwrok again.
Hope this will help u guys.
I can confirm athelon88's statement. I had tons of freezes when playing while logged into PSN. Now i log off from PSN when reaching the main menu after starting the game and i havn't had any freezes (neither load nor in game) so far.