As Marius discussed ( http://blogs.msdn.com/mariussutara/archive/2008/01/21/operations-manager-2007-sp1-tracing.aspx ) SP1 introduces some changes in SP1 to debug level tracing sometimes required when working with Customer Support Services (CSS) on issues
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Read the complete post at http://blogs.technet.com/cliveeastwood/archive/2008/02/22/operations-manager-2007-service-pack-1-debug-tracing.aspx