Your friend will likely have to start a Support Ticket with Customer Service through the 'Ask a Question' tab at NCsoft Support. Enough failed attempts will lock down the account entirely.
or
Call by Phone: Phone customer service for billing and technical issues from Monday through Friday, 12 noon to 5 p.m. CT, by calling (512) 225-6359 begin_of_the_skype_highlighting (512) 225-6359 end_of_the_skype_highlighting
Check out this specific issue from their support page. It lets you know the info they are going to need to help your friend resolve this.
Thanks for the info, Red Valkyrja! He waited a couple hours and it finally let him access his account, so all is well! 
Glad to see his problem was resolved.
Welcome back to the game for the both of you.
My friend and I just purchased the Going Rogue expansion and are re-activating our accounts. The problem is, my friend didn't remember his account name or password (it's been over 2 years since our accounts were active). After a few failed attempts, we managed to figure out his account name, but couldn't remember the password, so we used the "Forgot Password?" option to have a reset password sent to his e-mail. So far so good.
The problem is, every time he tries to log in to re-activate his account with the new reset password, the system informs us that there have been too many failed login attempts and to try again in a few minutes. After waiting an hour, he tried again, but the same message popped up. He tried having a new reset password sent to his e-mail, but that new one just brought up the same message.
Any suggestions or advice?