Vista - Edit or Inspect disk returns in error: There was a Problem parsingthe information returned by WMI

We are running Hyper-v on a HP DL360 G5 machine with Windows 2008 Core
edition

I manage the system from a windows Vista UK machine, both are in a
workgroup and I am logged in on the Vista machine as Administrator
with a corresponding password.

I can do almost everything from the Vista machine: Start, save,
shutdown machines, create new machines and add disks etc. but I am not
able to edit or Inspect an existing disk.

I get the message:
An error occured when attempting to retrieve the virtual hard disk 'D:
\virtual servers\machine name\Disk.vhd' on server HYPER-V

Getting the information for virtual disk 'D:\virtual servers\machine
name\Disk.vhd' failed.

There was a problem parsing the information returned by WMI.


End of message box.

I hope someone has a clue...