Event ID 4013 DNS-Server-Service on Network with Only One Domain Controller/DNS/etc

I'm consulting for a small business that has a single server that handles DC, DNS, DHCP, etc. roles. It is giving the following error with some regularity: 4013 DNS-Server-Service

The DNS server is waiting for Active Directory Domain Services (AD DS) to signal that the initial synchronization of the directory has been completed. The DNS server service cannot start until the initial synchronization is complete because critical DNS data might not yet be replicated onto this domain controller. If events in the AD DS event log indicate that there is a problem with DNS name resolution, consider adding the IP address of another DNS server for this domain to the DNS server list in the Internet Protocol properties of this computer. This event will be logged every two minutes until AD DS has signaled that the initial synchronization has successfully completed.

Any ideas on why?