Odd results when wurying a guest host with WMI

I am not sure this is the right forum, but has anyone come across this?

When i make WMI calls to a guest host to get CPU usage data i get odd results. Some negative #s and some over 100%.

The Negative #s seems to occur right after an hourly jump in the timer counter. I assume this jump is due to Vsphere synchronizing the physical clock with the virtual one.

On a machine with no other cpu usage I see this: http://i.imgur.com/ZA0xkfd.png   which makes me wonder if the adjustment lasts a while.

Thanks,

Ariel