External login for viewing rights

I am not entirely sure where to post it, so I have posted it hear hoping that someone can direct me in the right direction towards solving this issue.

I have a website where one has to log in before viewing certain aspects of the website. I would like to put my wordpress blog behind the login so that one cannot read it without logging in first. I store the information in session variables. However, this doesn’t seem to work – every time I get to the blog main page and print out the session variable, it’s empty. A strange thing is that it only fails in firefox, not within IE7. Yet another strange thing is that it doesn’t wipe the session variable – one remains logged in as it goes through other pages, but when it gets to the wordpress main page (and other subsequent pages), it says the session variable is empty. I was wondering what I could do so that I could get session variables to be recognized on the wordpress page.