I'd like to report some similar confusion and reinforce the solution by reporting my experience.
I also had the Host Name and Addresses part of the Configuration category in my server-manager page reporting:
A DNS forwarder has been configured. This means that all DNS lookups will be handled by the DNS forwarder. Hostnames and addresses cannot be modified on this server while a DNS forwarder is configured.
Looking at the solution offered here, I went into the Domains part of the Configuration in the Server Manager and changed just one of the Domains I had from "Internet DNS Server" to "Resolve Locally" and immediately I got my host name listing back in the Host Name and Address part of the Configuration category. All it took was to change one, I have several Host Names pointing to different ibays. I'd like to know what the difference is between the two "Internet DNS Server" and "Resolve Locally" settings. Is there some configuration where these settings make a more important difference? I have a dynamic DNS service providing reference to my DSL connection, dyndns.