I'm actually completely rewriting the account request handling for 1.13, which will migrate all the user data into cards.
I would try the workaround of recreating the correct name (as a basic card or something), renaming to something bogus, deleting, and then renaming the account request.
Thanks. I just tried that and still got:
Wagn Hitch :(
Server Error. Yuck, sorry about that.
Add a support ticket to tell us more and follow the fix.