This is an strange issue that we found recently.

Symptom:

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You have several Tasks scheduled. They all run fine until every Sunday at a specific time. The tasks after that time are no longer triggered, nor are there any errors given in the event logs. The Task scheduler service is still running, however no further tasks are triggered.

Cause:

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The problem occured after updated Windows Live Essentials 2011 by Windows Update.

Solution:

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The problem just occured after the SOXE task ran. After customers disable the SOXE task, ALL of others tasks start to run properly.

 

Reference:

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http://social.technet.microsoft.com/Forums/en-US/winserverManagement/thread/31349b83-c87d-425c-9059-eae7192fb850

http://social.msdn.microsoft.com/Forums/en/winserver2008appcompatabilityandcertification/thread/6fa3c7fa-511b-498d-9b37-1201e1ff2e59

http://social.technet.microsoft.com/Forums/en-US/winserverManagement/thread/28adff3f-7d08-4301-8337-50454679578a?prof=required

http://social.technet.microsoft.com/Forums/en-US/winservergen/thread/2faa4450-bcdf-46d4-934c-1f086a216ae7