iTunes and sort of off topic

Apple iPhone - iTunes and sort of off topic

I am trying to change my iTunes email address. Currently my iTunes id is my Gmail address and I'm trying to change it to my mobileme email address but when I try and change it the error says that I can not change to an existing mobileme address. Any idea what I need to do?

iPhone iTunes
I tried to do that once. You cannot use me.com apparently as strange as that seems. I had a heck of a time getting them to fix it.