What the fuck is this? My apple ID, which has existed just fine since, I don't know, 2002 now has to be an email address and Apple is telling me that my email address is already in use by another account? WTF, I'm pretty sure that yes, it's in use by the account that I'm trying to log in with.
Epic Fail, Apple.
Edit - it get's better, my account has been "disabled for security reasons".