I believe it is indeed an issue with the registration system. Raz had fixed something the other day, so it's possible something derped shortly after. Staff have been notified. Your patience is appreciated. <3 Hang in there.
As for your friend's username troubles, I'm not sure if the username changes are connected to the registration problem. If you'd like, I'd be happy to check our database for your friends' username and e-mail address via Private Message. c: