What would cause an orphaned ##MS_PolicyEventProcessingLogin##?
We upgraded two servers (from SQL 2000) to SQL 2008R2 using in-place upgrade. We started getting these messages in SQL logs after upgrade. We did not change this or any other logins or users during the upgrade process. 

My guess is upgrade process left two accounts (##MS_PolicyEventProcessingLogin## and ##MS_PolicyTsqlExecutionLogin##) orphaned.

EXEC sp_change_users_login 'Auto_Fix', '&lt;User Name&gt;' fixed this issue.