Got the problem fixed, thanks to some twitter help and the comments here. I’m doing a follow up to explain the solution.

http://support.microsoft.com/kb/810572

That’s always been the case when I get the user(null)/not associated with trusted connections error.

If I understand the post right, I think Tobias is on the right track. Assuming you want the “who cares” credential to be the person trying to use the service, I’d look at using Constrained Delegation and trust the service account your running your AppPool under to delegate credentials to that service. With constrained delegation you must specify the services that the trusted account will be used to access. There are some things that can get in your way like local security policies, your domain functioning level, and version of IIS. I’m also assuming you’ve toggled the ASP.Net ‘identity impersonate configuration setting.

Good Luck!

Hmm, my fear now is that I’ve been doing this in WinXP. Maybe IIS6/7 is different, what with the AppPools and all.

I did set the IIS process identity in IIS5, and that didn’t do the trick.

More info:
http://www.codeplex.com/WCFSecurity/Wiki/View.aspx?title=Intranet%20%u2013%20Web%20to%20Remote%20WCF%20Using%20Transport%20Security%20%28Trusted%20Subsystem%2c%20HTTP%29&referringTitle=Application%20Scenarios