Frontpage repeatedly asks for a password when I try to publish my website

I am using Frontpage 2003 (running on Windows XP SP2) to publish an internal company website.  The website runs on IIS 6 on Windows Server 2003.  In the past, when I published the website, I was prompted for an ID and password, and entering my domain ID and password would allow me to publish.  Now, Frontpage refuses to accept my logon credentials, and just repeatedly asks for them.  So far, this is what I have tried:
1.  I checked the Stored Usernames and Passwords on my local machine to make sure that it wasn't in there.  It wasn't.
2.  I followed the steps in Microsoft KB article 296645 (http://support.microsoft.com/kb/296645/en-us); that didn't help.
3.  I tried opening the production version of the website directly with Frontpage.  If I try to open it using the URL, I have the same problem as above.  I can open it by browsing to the file location, but when I try to publish that way, I get an error that says "The folder is contained by a server-based website.  To access this site, you must use the http:// url for the Web server."
4.  I thought the problem might have been caused by the last round of Microsoft Updates on the web server, so I uninstalled all of the February updates.  This also did not fix the problem.
5.  I had someone else try to access the site via frontpage from another machine.   They had the same problem.

Any suggestions would be greatly appreciated.