Difference between CPU Usage from Vcentre end and OS end - RHEL5

Hi,

One of the VM went unresposnive of RHEL5, while checking we found that CPU utilzation from Vcentre was 100%. In the same ref. we have rebooted it, while later on checking sar -A we found that it shows 90 % CPU idel dutring the same interval.

I would like to understand why there is descrepancy of both the details.

Thanks

Rajan