I just finished installing the latest version and followed your instructions for IIS7 setup.
I added the group Domain Admins as the allowed group to login to web console.
This works successfully with Firefox but IE9 gives error authenticating with the following results.
401 - Unauthorized: Access is denied due to invalid credentials.
You do not have permission to view this directory or page using the credentials that you supplied.
The exact same credentials are accepted on Firefox.