Try deleting site-related cookies from firefox and then logging in. It's really a mystery for me. I use firefox as my primary browser and indeed I would notice if it was not working right with this site. Login page does not refresh, if you are seeing this behaviour it means your authorisation starts but the system detects that your time of login stored in current session is older than time of your last logout so it assumes the session was stolen or broken and forces you to login again. This can't be possible if sessions are working right.