iTunes: "Your account was changed while you were editing your account information."
I could see a race condition causing this briefly, but if you get this error for more than 15 minutes, I would get in queue with Apple support:


http://www.apple.com/support/ios/contact/
http://www.apple.com/support/systemstatus 


Unless there is an outage, you'll likely need someone to assist you on the sever side to resolve these errors.