vmrun clone: "The Operation is not supported"?

Hi,

I am trying to clone a VM using vmrun with vSphere/ESX4 using the following command line:

    "C:\Program Files\VMware\VMware VIX\vmrun.exe" -T esx -h https://44.1.1.122/sdk -u root -p password clone "[datastore1] Win 2003 Template/Win 2003 Template.vmx" "[datastore1] Win 2003 Template-X/Win 2003 Template-X.vmx" full

but I get the error:

    Error: The operation is not supported

What about the operation is not supported? I haven't seen anything that suggests that ESX4 doesn't support clone.

Thanks ahead of time.

CC