We haven't migrated to 2k8 yet, so I haven't had the pleasure of indexing 2k8 logs, but looking at group policy documentation for 2k8 R2 the following sticks out:
Machine, wdi.admx, Diagnostics: Configure scenario execution level.
Determines the execution level for Diagnostic Policy Service (DPS) scenarios.\n\n\nIf you enable this policy setting, you must select an execution level from the dropdown menu. If you select problem detection and troubleshooting only, the DPS will detect problems and attempt to determine their root causes. These root causes will be logged to the event log when detected, but no corrective action will be taken. [...] The DPS can be configured with the Services snap-in to the Microsoft Management Console.
What execution level do you have the Diagnostic Policy Service (DPS) set for? Could it be that it's configured for detection and troubleshooting, and causes it to log the extra data?
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FYI 2k8 r2 group policies: http://www.microsoft.com/downloads/details.aspx?FamilyID=18c90c80-8b0a-4906-a4f5-ff24cc2030fb&displaylang=en
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