Bane, read my last post above; then open your Vbulletin board and look at the address in the URL box.
http://www.influx9.com/index.php
Then go to your VBulletin Forums Admin Control panel and look at the URL there:
I don't know what it is, but it will be different.
I think that difference may have the clue you need.
I am not familiar with the code you use to change the web pages (i.e., php? action=forums), but it is really cool. Is that or is your directory structure (archive not being in the forums folder) making a problem? Too early for me to tell, though others probably could. But before wondering any more do what I just had to above.
I am far less expert than the others around here, but I hope that this may help.