Thanks for your quick reply, POCEH.
Let me give some more background information. The VM is on an external USB drive and I can boot the VM fine once connected to my laptop.
I use Converter from within a different VM with the USB drive connected to a QNAS networked storage device. I successfully converted another VM that was on the same drive this way. Can you give me a tip on what I can do to verify the VM copy, other than booting it and making sure that it runs without problems on my VMware Fusion?