As LordS suggests the best thing you can do is to write a PM to Delay or Red.
Also since there is alot of players sending the admins PM's everyday, you might have to have patience when waiting for a reply.
It's hard to say what the problem is: if the account has been de-activated somehow, and that it's not possible to re-activate? Are you sure he has the right password? Or that he spelled his nickname the right way?
Good luck and I hope you and your friend will figure this out. Othervise I suggest you wait until the registraion opens again and create a new account.
Cheers~ // Shallow