SQL Server 2012 Login Failure As of this morning we have had thousands of failed login attempts to our SQL Server 2012 box. 

Error :


  Login failed for user 'Domain\User'. Reason: Infrastructure error occurred.
  Check for previous errors. [CLIENT: 10.xxx.xxx.xxx]
  
  Error: 18456
  Severity: 14
  State: 1


I have checked all the logs, permissions, and scoured forums for help on this issue but to no avail.


  Server Login &amp; Database User accounts are enabled
  Server Login is mapped to the database that it has access too
  Windows &amp; SQL Server Authentication is applied
  SA account is enabled
  No orphaned users
  etc etc...                    


Any ideas ?
The box lost connection to the domain controller, hence the login issues