I have this same problem with vbadvanced also.....
i have set up a link for the classified section at
www.arbtalk.co.uk/forum but when you get to the classifieds you arent logged in anymore. typing in your details takes you to the "thankyou for logging in " message but then when it directs to the classifieds you're still not logged in....however if you navigate to somewhere else on the page you are!
any help appreciated, thanks