IsAuthenticated?

Issue: Form Based authentication, authenticated state cannot be kept between pages navigation in a web application.
The sample web app has been tested on a w2k svr which is a domain member and worked fine.
Moving to a stand alone w2k- my home PC, it failed. Trace file indicates the credentials has been authenticated (FormsAuthentication.Authenticate). On page redirection (FormsAuthentication.RedirectFromLoginPage(txtUserName.Text, false);), the authenticated state lost.
Having run the IIS authentication diagnostic tool (http://www.iisfaq.net/), I found it point to the fact the IIS Web Server needs to be a domain member.