OK, so on top of the registration problem - do NOT go to your profile, and edit account settings re: changing your e-mail or password.
Because if you do, the system asks you to re-authenticate your account.
And because the system can't generate e-mails - you can not re-authenticate!
I just found this out on another account (Yes, I have two).
So just sit tight until we get this thing updated!
(Changing signatures is OK, just not back-end stuff.)