OCS front end service fails to start after KB967831
KB967831 patch will try to update OCS and afterwards will try to start RtcQmsAgent (aka Monitoring Agent)
If you dont use or configure this service it will never start, causing the rollback of the patch and with it the failure of the frontend service.
So just install MS messaging queue services (ServerManagerCmd -i MSMQ-Services) and MS messaging queue server (ServerManagerCmd -i MSMQ-Server) and reapply the patch that will apply with success since now he is able to start Monitoring Agent Service.
Source for this information: http://blogs.technet.com/exchangept/archive/2009/05/21/ocs-front-end-service-fails-to-start-after-kb967831.aspx
This solved my problem in my LAB ;) …… all the server are setup to update automatic ………… UPS “MS Update”, where did you test this patch before rolling it out to the public !