I have excatly same problem with the difference that my username mail address is an old one that does not exists anymore (which is an old GW1 account linked to GW2) and I have my current mail address on my account place.. but the validation mail says it will send it to my old mail which troubles me. and Like Sipso when I try tell it to send it on my current mail it says that email address is already in use
edit I have sent a ticket about it and had a automated message that didnt have anything to do with my problem. then I updated the ticket with additional details and I got a reply a long time later telling do this and that but it was obvious the one who addressed my ticket didnt seem to read what was my problem