Tips & tricks:
(1) When using Mozilla Firefox check your browser settings under "Extras > Settings" regarding
(2) It is possible that cookies cause a concurrent logout during the login-process. In that case clear your cache and cookies.
- Mozilla Firefox: Extras > Settings -> Private data button "Settings", click the checkboxes "Cache" and "Cookies", click "OK" and "Clear now", subsequently. Confirm with okay "OK".
- Internet Explorer: Extra > Internet settings > Main > clear cookies.
(3) Problematic could also be several "Plug-ins" (which possibly installed themselves). It might be that there is a plug-in that causes after a very short time the site to refresh again, which finally ask for a relogin. In that case, please check your list of plug-ins.
(4) Another, possible, but not imperative origin of the problem might be the firewall, that you are probably using. A delicately one could be e.g. "Zonealarm", when it was set strongly.