Well, Dreighton and the others at this year's Dragon*Con convinced me to let my son signup and play so we tried to do it tonight.
First, he created the handle Bulbarakh Tlakh`sar, and received a message saying the handle was already taken. Since I was so surprised by that, I had him try again to the same result so I investigated and sure enough, there is already a character by that handle that last logged in Year -1 Day 365 (?).
Next he tried the handle Sakhisabul Tlakh`sar and received the message that the email address had already been used to register for an account. This is of course from his earlier attempt. The email address is firstname.lastname@example.org
Well, since you already signed up at Dragon*Con, that account still exists so you are free to use it to continue playing :)
If you can't remember the password, please use the Lost Password feature with the signup email and the handle you used at Dragon*Con.
There is no account with the handle Bulbarakh Tlakh`sar.
There is no account with the e-mail address email@example.com.
I am not sure why he would be receiving the message that the handle is in use unless he accidentally submitted the form twice, but either way it looks as though the requested account must have been declined and he should be able to register again.