Oh it brings up the IIS Windows Authentication prompt. It does this even when the site is in the Intranet or Trusted sites list? I've heard of situations where this has happened but haven't been able to recreate it. I'll see if I can find a solution tomorrow but in the meantime maybe try clearing any cookies/cached files from your browser.

Just to clarify, when you're already logged in via the WindowsSignin page as you mentioned in the first paragraph, is the Login button still showing on your portal or does it look like it does her on the DNN site [Your Name] | Logout? Or do you have an Account Login module somewhere on one of your pages and that's what is blank. If it's the latter then that's normal as the account is already logged in so the fields are hidden.

Before you get too far into customization of the AD settings let's leave Hide Controls unchecked and don't put anything in the IP range textbox. Clear you cookies/cached files etc. and then hit the site. Ideally you should be automatically logged in or, at minimum, get the IIS Windows Authentication popup. If you go directly to the main page then it sounds like you haven't got the <add name="Authentication.../> uncommented in your web.config under <httpModules> (the last one in that section not the first one).

I'm about to shut things down for the night but will check the forum when I get to work in the morning as I normally do.

Okay now I know where we're at. I'll have to check my email at home as someone else had a similar problem and emailed me when he got it fixed. He ended up having to apply a patch from Microsoft on his server and change a setting or two in his internet options but I can't remember what they were. Hopefully I still have his email.