Or you could try what me and my friend did,seems to work fine
wipe all the data from your ps3 (seeing as you already own the orginal disc and this is for backup use)
put the disc in and play from the disc until you go into the safe zone with everyone else,save the game,install to the ps3 HDD (or external i presume)
take disc out load your game from past the arena escape with katie.....
we didnt use the patch or anything like that and my mates still playing it now with no problems