As documented in CTX106455/WMI_Guide.pdf

"To display information about MetaFrame Presentation Server computers and server farms using a WMI consumer, you must have access to the Root\Citrix namespace in the WMI configuration. You must also have the appropriate Citrix administration rights to display information about servers and server farms.
If you delegate areas of MetaFrame Presentation Server administration and server farm management to MetaFrame Administrators, these administrators can monitor and control only the specific administration tasks that they have permissions for."

For example the following code will return an error 0x80041001 when run as a non-Citrix Administrator:

Set objWMIService = GetObject("winmgmts:\\.\root\Citrix")
Set colItems = objWMIService.ExecQuery("Select * from MetaFrame_ICA_Client",,48)
For Each objItem in colItems
wscript.echo objItem.ClientAddress
Next
Set objWMIService = Nothing
Set colItems = Nothing

The default WMI permissions appear to be suitable. To check or update:

- Select Start | Run
- Enter WMIMGMT.MSC and click OK
- Right click on WMI Control (Local) and select Properties from the context menu
- Select the Security tab
- Expand Root
- Select Root | Citrix
- Click the Security button
- Set permissions as required

To apply the appropriate Citrix Administrator permissions:

- Start the Citrix Access Management Console
- Select Citrix Resources | Presentation Server | <Farm> | Administrators
- Right click on Administrators and select New | Add Administrator from the context menu
- Select the appropriate Citrix User or Group and click Add
- Click OK
- Click Next
- Click Next on the Contact Details dialogue
- Click the Custom radio button and click Next
- Select <Farm> | Administrators
- Uncheck Log on to Management Console
- Select <Farm> | Servers | Sessions | View Session Management
- Click Finish

Note: Different WMI queries will require different Citrix Administrator permissions. These permissions allow the sample code above to run.

Provider for Microsoft WMI Administrator's Guide
http://support.citrix.com/article/CTX106455