SharePoint 2010 web server, on Windows 2008 R2. An error message appears in the server Application event log:
Source: SharePoint Foundation
SQL database login for ‘SharePoint_ConfigDB’ on instance DATABASENAME failed. Additional error information from SQL Server is included below.
Login failed for user ‘NT AUTHORITY\ANONYMOUS LOGON’.
Error message repeated once a minute.
After rebooting the server, the error went away.
I’d love to be able to explain this, or say the discovery of the solution was a result of my genius. Sadly, no. After several days deep-diving the logs and exploring the breadth and depth of the blogosphere to no avail, temporarily disabling various timer jobs that appeared in the logs just prior to the error message, and chasing dead ends, it was a power outage and a failure of the backup power supply which forced the server to be restarted and made the error disappear.