Topic: Session is not alive

For some reason after 2 requests session object is becoming nil.

1.before_filter :login_required
2.login_required checks for session[:user_id] and redirects either to login page or home page of app
4.Entered credentials in Login page and home page is launched (This is a redirect on server)
3.Any link clicked on home page takes back to login page as the session is nil at this point.

Any clue ?