I recently promoted a server to a domain controller (DC), and now my event log reports an SPNEGO (Negotiator) event. What’s causing this error?

If this event (event ID 40960 or 40961) appears only once in the event log, you can ignore it. The error occurs when the File Replication Service (FRS) starts before the directory service. If the error persists, you most likely have a problem with the directory service and should start troubleshooting Active Directory (AD).