If (and I think is true) both datastores can be seen from the same ESX Server, you can connect with the vmware client directly to the ESX and copy the VM files with the browse datastore. Don't forget to remove the VM from the inventory and re add it again when the copy/move is done.
Marcelo Soares
VMWare Certified Professional 310/410
Virtualization Tech Master
Globant Argentina
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Marcelo Soares