Depending on when you made your account on the forums, this:
http://www.eqemulator.net/forums/viewtopic.php?t=14010
may or may not apply to you. If you made your account before the date in that thread, then your forum username and password should work. If you made your account after that date, then you must activate it by following the directions in that thread before you can logon to EQ with your account.