Resolution:
If you install an Engine Daemon to run as a Service and the Service logs in as another user, the CPUIdle mode will not work correctly, because the Engine Daemon will not be able to retrieve performance data (such as CPU information) from the OS.

To remedy this, do the following:

   1. Start regedt32 (Open the Run... box from the Start menu, and type regedt32.)
   2. Navigate to the key HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsNTCurrentVersionPerflib
   3. Right-click the folder named Perflib in the left-hand pane and select Permissions... or select the folder and from the Security menu select Permissions....
   4. Add the user that the Engine is logged in as, and grant Read access.

This process must be done for each Engine in the grid.

Novell has a free utility that can let you script permission-setting in the registry that works for remote machines as well. It can be found at http://www.novell.com/coolsolutions/tools/1129.html. The following command line works for changing the key:

regperm /k "HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionPerflib" /e /a:datasynapsetest:r /i

CPUIdle mode doesn't work with Engine Daemons running as a Service