I administer a Win 2K/2K3 air-gapped research/educational network. Until recently, the FTP server (2K3 Web. Edition, on the forest root) allowed seamless anonymous logins for any user who browsed to the FTP site.
Now, anyone who browses to the FTP site is presented with a login dialog, for which any and all credentials do not work.
In IIS manager, "anonymous" and "anonymous only" are selected. The unsuccessful anonymous login attempts are answered with "Either the server does not allow anonymous logins or the email address entered is invalid.)
NTFS permissions are OK.
The IUSR_<servername> account appears to be as it should.
What may have caused this to happen, and how might I remediate it? (All my drilling down so far has just described how to set up anonymous access, which, of course, is done. As far as I can tell).