Restricted area redirect problem

My forum has a restricted area (Committee members only), while the site can be accessed via either of two domains and the server is set to cope with people entering the wrong number of "w"s in the URL (eg, w.pedalcars.info, wwww.pedalcars.info, etc).

I've recently introduced a site-wide script that detects a wrong number of "w"s (ie, other than three!) or the use of the secondary domain and immediately bounces the user to the primary domain (www.pedalcars.info). The script also retains the remainder of the URL including any query string, so you still get the page you were after. This is so any bookmarks set or links emailed are of the primary domain.

It works perfectly, with the exception of the committee area, where, if you type in an address that gets bounced in the manner above, you get told you aren't allowed to view the page - even if you were looking at it before and, say, deleted a "w" from the start of the URL.

It's almost as if it logs you out (but it doesn't - and you can get back in with two clicks).

Any ideas?