The GUI page has changed in recent versions and we need to change the agent message to point to the correct place. Its Adminstration>Server now (I wrote up BZ 783997 for that).
Read the high availability wiki page for the full details on this. for your specific error, the server is advertising itself on a bad hostname that your agent cannot DNS resolve (ubunturhq4.2 - that is not a hostname your agent can resolve to a proper IP address). Change the public endpoint address of your server. Read the following sections on that high availability wiki page for details: