Update 2:

No, it's still happening but only when I log in.

I deleted all cookies and entered the board logged out. I could access through both cgi-bin & php links. As soon as I log in the php link returns a 404 error.

Main:
http://www.audiotoolsdirect.com/cgi-bin/ubb/ultimatebb.cgi

Accelerator:
http://www.audiotoolsdirect.com/ubb/ultimatebb.php

Very strange. <img src="https://www.ubbcentral.com/boards/images/graemlins/confused.gif" alt="" />