- Is running as an account other than NetworkService
- or isn't being accessed via the server's AD name (eg through an alternate URL, or load balanced alias)
In both cases getting the right SPN added into AD will fix things, but sometimes this can be problematic. However you can explicitly downgrade the virtual directory to only use NTLM authentication by setting the NTAuthenticationProviders property. There's no UI for this, so you have to set it on your IIsWebVirtualDir in the metabase, eg (for IIS 6 \ Windows 2003):
Then everything (?) works again. Hooray.
cscript C:\inetpub\adminscripts\adsutil.vbs //nologo SET W3SVC/1/Root/MyApp/NTAuthenticationProviders NTLM
This is discussed at the very bottom of this article: http://support.microsoft.com/kb/215383
NB: For Windows 2000 you can only set this at a site-level, not an application level, as the article outlines.