The only fix to this might be that you actually need to do a full account reset from the user panel.
It's not really something suggested at all since it will remove everything from your account, but throughout the times, when this sort of bug or glitch has arrived on peoples account, they've have been unable to log in at all until this has been cleared, and even in some rare cases even that doesn't work, leaving the account crippled stuck on the character selection screen.
Why this happens I honestly do not know, but when you think of it quickly there's a lot of information on the server, things like your characters, your friends, your groups linked to all the characters, the things your character wears and what not. Though similar things has been said before, when users have been deleting friends and all of a sudden the account is not working anymore.
I'm afraid though the only suggestion I'd be able to give at this point is to do an account reset since it has proven to work before a few times, but I give not guarantees.
