[Login bug] Bad redirect

After typing valid login and and password and submitting it, I get following error:

== Error start ==

The page isn’t redirecting properly

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

*   This problem can sometimes be caused by disabling or refusing to accept cookies.</i>

== Error end ==

My browser is set to accept any cookies from localhost. Please help.