My guess is that WMI couldn't be connected to using the "root\cmv2" namespace. You can see what I mean if you go to your start menu and type "wbemtest" and press enter. Then press the "Connect..." button, a window will popup and click the "Connect" button without changing any of the field. On a well configured computer that dialog will disappear and you'll be properly connected. On a misconfigured computer an error will show.
If an error was shown (or even if it wasn't shown) this WMI Diagnosis Utility will help you diagnose the problem.