I am getting this same error. I can get to the forums admin from the site admin area, and then when i click forum index from the bb admin area it shows admin online, but when I try to enter a forum it sends me back to Your Account. And when I click forums from the main site it don't show me online. Mabe you can get a better idea by taking a look.

http://www.cheat-shed.com/CS/index.php

Any tips, mods ect will be greatly appreciated
mike