Simple referral question

I have an HTML home page which is built with webtemplates but i cant seem to get the refferal link in the menu to work when i click forum.

Home page
http://www.gamblingforums.net

Forum
http://www.gamblingforums.net/vbportal/forums/index.php

Link in menu
http://www.gamblingforums.net/vbport...s/index.php?s=$session[sessionhash]

But if i do this
http://www.gamblingforums.net/vbport...p?referrerid=1

It works fine.

Any thoughts?