Hi, Patrick.
IIS defines a number of different 401 errors
that indicate a more specific cause of the error. :
401 - Access denied.
401.1 - Logon failed.
401.2 - Logon failed due to server configuration.
401.3 - Unauthorized due to ACL on resource.
401.4 - Authorization failed by filter.
401.5 - Authorization failed by ISAPI/CGI application.
401.7 - Access denied by URL authorization policy on the Web server.
This last error code is specific to IIS 6.0.
It might be that you have to take *those* into consideration
if you want a *specific* error code captured.
I'd try using 401.1 to test catching a "logon failed" exception
Mind you, it could very well be that Windows Integrated Authentication
preempts any IIS authorization scheme.
Maybe testing if the 401 exception works with Forms Authentication would
help us find out if Windows Authentication does preempt IIS's authentication.