I have tried installing manually with the .rpm and by pointing the host to the yum repo and I still have issues getting the error. To the best of my knowledge the firewall is not standing in the way. Our Windows hosts are all checking in fine. The agent is initiating the communications, the poller hostname matches, as well as the port. The username is correct and so does the password (AFIK, how can I verify it's using the correct credentials?), no proxy is required.
