clone vm issue

Hi,

I am getting error when try to clone a server as below

LocalizedMethodFault Object

(

  [fault] =>

  [localizedMessage] => The operation is not supported on the object.

)

I am following https://www.vmware.com/support/developer/vc-sdk/visdk41pubs/ApiReference/vim.VirtualMachine.html#clone

I have ESXi 5.0 .