I have started getting the above error message now ive started developing ASP

I set restricted access to pages- but no matter what I cannot log in (i have
followed my DW ASP book word for word on this, also Fordwebs tutorial!!) I can
find no reason for the user authentication server behaviour to not be
working... If the error3 message is the problem(?) how can i fix this problem?
(would prefer not to do a fresh install but hey..!!!!