I don't know if this is the case with your situation, but I have hyperic monitoring some machines that are in a remote office location. To get these machines monitored by the Hyperic server that is in another office, I had to poke some holes in the firewall for these machines and open up port 2144 so that the data would come across. Also, make sure that you used the correct ip addresses when installing the agent.
When you installed the agent, did you choose for the communication to be secure or unsecure?
