We have seen this issue and found that, provided your virtual center server is connected to the doamin, that a re-boot of the virtual center server appliance has resolved this.
We are a VMware Reginal Academy: www.cccti.edu/vmware, and had this show up when using the 5.1.0/5.1.0b versions.
One other issue we have found also is that the virtual center server appliance will not maintain the FQDN without performain a re-boot.
Hope this helps.