Symptom: Connecting to via FrontPage returns errors. It does not even prompt for login ID & Password.
Workaround:
1st ) You must make sure your FrontPage extension is turned on via your control panel. If you've done that and still unable to connect, please try uninstall and reinstalling FrontPage extension.
2nd) If you are still unable to connect via FrontPage after the previous solution, this is most likely because you are being a proxy server. To work around this, you can do the following:
go to your Control panel -> Site Admin -> Set Basic Authentication and set your FrontPage url to basic authentication. This will resolve your problem.