"A referral was returned from the server" from ActiveDirectory plugin

OK, I fixed it... There were 2 problems:

1. I needed to use the fully qualified name, e.g. Source=ServerFault.com (as suggested by squillman)

2. I needed to change the "Anonymous Access" user in IIS to be a network user that has access to Active Directory (previously, it was a local machine user)

Thanks all who helped!

Directory referral messages often indicate that you're either binding to the directory in the wrong place or that you're doing some kind of cross-domain query against a server that might be in the same forest but isn't responsible for the domain in question. What are you using for the Source configuration tag? Do you have a domain controller at the site where your server is that is authoritative for that domain?