WebDAV on Windows 7 "the folder you entered does not appear to be valid":

Trying to "Add Network Location" in Windows 7 64-bit in order to connect to my WebDAV server on a local Ubuntu Natty 11.04 32-bit server (running Apache / mod_dav).

I get an error "The folder you entered does not appear to be valid. Please choose another".

So far as I can tell I'm doing everything correctly. I can open the location in Firefox just fine.

The server configuration is almost identical to another WebDAV server I've setup in the past, AND my Windows 7 machine can connect to that other webdav server just fine.

The relevant part of my apache config:

        # WebDAV support
        Alias /webdav "/var/www/asdf"
        <Directory "/var/www/asdf">
            Options Indexes FollowSymLinks MultiViews
            Dav On

            # allow from all IP addresses
            Order Allow,Deny
            Allow from all

            # require proper authentication
            AuthType Digest
            AuthName testrealm

            # You can use the htdigest program to create the password database:
            #   htdigest -c "/etc/apache2/webdav.digest" testrealm johndoe
            AuthUserFile "/etc/apache2/webdav.digest"
            AuthDigestProvider file

            Require user johndoe

        </Directory>

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I've run the htdigest program to generate the digest file:

htdigest -c "/etc/apache2/webdav.digest" testrealm gordon

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It works fine to connect to it via Firefox or using the "WebDav Navigator" free app for iPhone, or using the Pages app for iPhone.

But, when I try to connect to the server in Windows 7 by creating a "Network Location" in My Computer and specifying the URL:

https://remote.mydomain.com/webdav

I get the error "The folder you entered does not appear to be valid. Please choose another"

My SSL certificate is correctly installed and issued by GoDaddy.

Not sure what to try next here... any ideas?