What is the correct configuration if only the login page needs SSL?

[X-Killer]

I've written a website with a login page which uses forms authentication
against a username/password table. I've configured the web.config with
forms authentication and with loginUrl="login.aspx" in web.config and
doesn't accept anonymous login. The application runs normally as expected.
However, when I change the loginUrl="https://somewhere.net/Apps/login.aspx",
the famous grey 'Windows Login' box pops out instead of my login.aspx.

It seems that my server thinks that I'm redirecting the login page to a
remote server but I'm certainly not.

Any comment is appreciated. Thanks in advance.

 

[Tampa.NET Koder]

Make sure IIS authentication settings are not overriding the web.config
settings. Also check folder permisisons.