By default, Internet Information Server uses a NT Challenge and Response authentication scheme for all web sites on the server. When your site (or a directory) is password-protected (removing the Anonymous access), you essentially switch over to this authentication scheme. Netscape, unlike Internet Explorer, does not recognize the NT Challenge/Response authentication scheme.

To make your password-protected directories accessible by Netscape Navigator, contact Technical Support to enable Basic Authentication (Clear Text) and disable Windows NT Challenge and Response.