I keep getting my game saves corrupted on PS3. Very frustrating.

I don't know if anyone out there has been having problems with their games saves being corrupted. I own Ratchet and Clank. I played about 75% through it and my game saves got corrupted. I figured that it was my error, so I started playing the game again, and this time it got corrupted about 25% into it. Another game I have is the Simpsons. Last night I was 59% into the game, and then today the game save date is corrupted once again, which means that I will have to start over again. This is extremely frustrating. I do wait until the game saves before shutting it off. Does anyone else have this problem??? Is there a website where you can download a game save, and I am not talking about 100% completion game save but one where you can pick up the game half way through??? I enjoy these games, but I really do not want to play these games yet again from the beginning.