Have you ever seen the following error in the SQL Server Agent error log:-

Message
[425] delay_between_response attribute (10 sec) of alert (19) is less than poll interval for this alert (20 sec)

This means that the Agent is trying to respond to events in the event log every 20 seconds, but it is firing every 10 seconds. See http://www.sqlservercentral.com/articles/Administration/3177/

 

If you want the messages to go away alter the EventLogPeekInterval registry setting:-

 

-- Script to alter the needed registry key DECLARE @RegValue INT
SET @RegValue = 10 -- provide dec. value in seconds between 10 and 3600 EXEC xp_instance_regwrite @rootkey='HKEY_LOCAL_MACHINE',
   @key=N'SOFTWARE\Microsoft\MSSQLServer\SQLServerAgent',
   @value_name='EventLogPeekInterval',
   @type='REG_DWORD',
   @value=@RegValue