Of course it won't let you play.. You need to update to that 5.55 firmware.. Hopefully, when Final Fantasy Dissidia ISO comes out it won't be the same..

I've read somewhere that when they make the games in japan for let's say when 4.0 firmware was running, when they port it to the U.S. version, it's still coded for 4.0 firmware. Not with that crap that detects if your running OFW or CFW...