vmclone.pl errors

I am using following spec to customize the guest OS with vmclone.pl, but keep getting errors:

/usr/lib/vmware-vcli/apps/vm/vmclone.pl  --vmhost vm-23. --vmname sdktest-01  --vmname_destination sdktest-23 --customize_guest yes --filename /root/cus_vm.xml

Fault
SOAP Fault:
-----------
Fault string: A specified parameter was not correct.
spec.identity
Fault detail: InvalidArgument

# cat /root/cus_vm.xml

<Specification>
   <Customization-Spec>
          <Auto-Logon>1</Auto-Logon>
          <Virtual-Machine-Name>TestVM</Virtual-Machine-Name>
      <Timezone>140</Timezone>
          <Domain>domain.com</Domain>
          <Domain-User-Name>username</Domain-User-Name>
          <Domain-User-Password>password</Domain-User-Password>
          <Full-Name>admin</Full-Name>
          <Organization-Name>companyname</Organization-Name>
   </Customization-Spec>
<Virtual-Machine-Spec>
      <Guest-Id>centos64Guest</Guest-Id>
      <Memory>2000</Memory>
      <Disksize>43423944</Disksize>
      <Number-of-CPUS>1</Number-of-CPUS>
  </Virtual-Machine-Spec>
</Specification>

in Vcenter5, I saw " A specified parameter was not correct. spec.identity

Can someone shed some light?

Thanks.