I don't know much about hacking things on the Iphone, but I used to do a little bit of hex editing and things back on my Xbox 360. Whenever you hit 2,147,483,647 or over, the game would freeze, crash, or you would end up with negative numbers. I believe this is the reason the Attack works, but the health doesn't. Since the attack is independent for every character, but health is shared, your health goes over that number. Pretty sure if you could lower the health values where they would be lower combined than 2,147,483,647 , it might actually work.