Mallion

What has worked for me is the followingssequence: First you have to have your Portal 2 game on the PS3 linked to a Steam account.

With that done, when the save loop happens hit the "PS" button on the center of your controller & sign out of PSN. Next hit "PS" button again to be returned to your game. If not already on the pause menu, press the "Start" button. Now press "Select" to bring up a Steam menu. Using it to log back into PSN will break the auto-saving loop & allows you to then make manual saves. This should stop the auto-save glitch until you shut down the PS3. Next time you start the game you'll have to do it again. So far this is all I've found that works. Hope it helps!