Chances are its not firewall related at all, but rather a filtering or blocking program that your employer installed to restrict various web sites that are not related to your line of work. Its quite common for all discussion boards to be blocked, as they are not deemed productive? These type of server based apps filter out the whole domain: www.flyertalk.com and all sub pages. Ask your MIS folks if they use such an app?

If it is firewall related, try setting your browser to accept all cookies from any server?