ZOMG continuity error!!!1
Also, the kryptonite on the island should have hurt him. That shit was sagging right in front of his face. He collapses after just being exposed to a little bit of it (see: first couple films). I dunno. I really didn't like that about the new one.
His kid wasn't effected though. I thought that was a cool addition to the film. I wonder if they'll make one with the kid grown up, super-esque, and immune to kryptonite.