Morph Mod Problems

So I just got my skin working with 1.7 versions, but now whenever I try to kill a mob or try to morph into one, it kicks me out to the server list with the error "A fatal error has occurred and the connection has been terminated." And then corrupts the world. It might have to do with the fact that the file is still 64x64 and I just moved everything up. I would really like help, otherwise, I might not be able to play on my modded world again. (I did the tests on other, non-main worlds.)