Windows 7: WebDAV issue

Hi all,
I am a newbie to WebDAV and was from what reading I have done have being able to see that I can host calendar, contacts and also some file share with it so that I can sync it with my iPhone but when I try to connect to the web dave share via localhost (on the server) I have no issue and will upload the outlook calendar but when I try to hit the dns name/address it will come up with a authentication prompt box, I enter the login details but then the pro pmt comes up again, and so on. Once I have being able to get it to error saying that access is denied but I can't work out why as I am using the same credentials as the login I am logged in as and not typing incorrect. Does anyone have any suggestions?