Hi,
Your convertion path is not supported directly.
page 16 of VMware Converter Standalone 4.0.1 guide:
Converting and exporting virtual appliancesYou can convert and export virtual appliances stored in Open Virtual Machine Format (OVF and OVA). You can import a virtual appliance to run in anexisting ESX host or Workstation virtual machine, or you can export an existing VMware virtual machine to an OVF virtual appliance to share over the network.
page 21, Virtual Appliance Conversion Limitations
Although Converter Standalone does not support the preceding scenarios, in each case you can use ConverterStandalone to first convert the source machine to a VMware virtual machine and then convert that machine to a virtual appliance.