[Zope] No ZMI - panic!!!!

I'm trying to update a Zope site which I set up some time ago but can't get the ZMI to start up. Any ideas on what to do? When I try to acccess http://mysite:8080/ I get - Zope Site Error. How do I force a login prompt or include a login in the URL? If this is a FAQ, please tell me which Q to look under. -- John