I hate it when people think they know more than you when your in the mix of things and have been fighting the problems for more than they realize... But just in case.... here I go being the person I hate.

Could you point forums.coade.com to 65.57.255.42 with an A record DNS entry? Then find replace query in your mysql db to match everything up? Even replacing the newly created ip unmasked links as well?

Of course you'd be very granular
http://www.coade.com/ubbthreads/ubbthreads.php
to
http://forums.coade.com/ubbthreads/ubbthreads.php

http://65.57.255.42/ubbthreads/ubbthreads.php
to
http://forums.coade.com/ubbthreads/ubbthreads.php