Found this on another forum earlier mate...

"Think I've solved the problem!!!

Found it on a quiet little gaming site after searching all day. Wipe out your save data (including the auto save) and the installed game data. Switch off the console and disconnect the power as well. Then restart as normal but DON'T connect to the internet. Install the game as before , making sure you're not net connected...this seems to be the source of the corrupt install file as I noticed when I did it the last 3 time sthat my router was going haywire with PS3 traffic. I also made sure the autosave feature in the game is also disabled as this was recommended as well. Just had it on 4 hours and not a single crash or even a stutter in the frame rate! Superb!!!"