I found this error last week during a deployment in a customer. The vCenter Infrastructure Navigator appliance does not maintain its configured hostname after a reboot, it gets reset to the default localhost.localdom value.
Setting it again in the administration web interface doesn’t solve problem, it will be lost again after the next reboot.
The problem is in the vami_set_hostname script, it has a HOSTNAME variable set to localhost.localdom and if it fails to make the reverse lookup of the hostname from the IP address using the host command it will be set to the default value.
To fix this edit that file, it can be found on /opt/vmware/share/vami, and set the value of the variable to your hostname. After that reboot the appliance to check that everything works as expected.