carnold have you reviewed the agent logs on an affected endpoint to attempt to ascertain why they are no connecting to the ePO server? By default on a 32-bit machine this will be C:\Documents and Settings\All Users\Application Data\McAfee\Common Framework\DB\Agent_<computername>.log and for 64-bit systems C:\ProgramData\McAfee\Common Framework\DB\Agent_<computername>.log.
I can only assume that there hasn't been any changes to the DC that has the ePO installed e.g. IPv6 enabled, new network interface installed, host name change, network routes/firewalls etc. McAfee Agent attempts to connect to the ePO in the order of last known IP address, DNS name, or NetBIOS name, so in theory if you haven't changed the IP address of your ePO then endpoints should still be able to communicate.
You might also want to check that there is no conflicts with a possible new component installed on your existing DC and the ePO communication ports.
So, i rebooted the primary DC due to windows updates and everything started working....