Enabling Windows Performance Monitor in CF8

Platform: Windows 2003 SP2, CF8 Standard (upgraded from CF7)

I can't seem to get the Windows Performance Monitor Counters for CF8 to work in my newly upgraded installation.

1) In CF Administrator > Debug Output Settings I tick the "Enable Peformance Monitoring" option and click Submit Changes. Message: "Server updated" appears and the box remains ticked. However If I refresh the page or navigate to another and return, the tick is lost.
2) Restart CF Service
3) Open Perfmon and click Add Counters
4) ColdFusion 8 Perfomance Object and Counters are all listed correctly, BUT there are "no instances" in the box on the right and therefore the "Add" button is disabled, so I can't add any counters.
5) Checking in CFAdmin again, the "Enable PM" tick is still lost.

It all worked in CF7, however that was on W2K3 SP1.SP2 is a new factor, could that be the cause?

Thanks.