Warning: your browser doesn't send the HTTP_REFERER

hej när jag skall logga in på vissa forum sidor så får jag upp denna lilla grej

"Warning: your browser doesn't send the HTTP_REFERER header to the website.
This can be caused due to your browser, using a proxy server or your firewall.
Please change browser or turn off the use of a proxy
or turn off the 'Deny servers to trace web browsing' in your firewall
and you shouldn't have problems when sending a POST on this website."

jag använder firefox och norton antivirus 2003
någon som kan hjälpa mig :S