It will be a configuration issue with the .INI file. I've seen this before. As you've noticed, it won't be getting as far as validating the network name or running the OVF Tool command and creating a log file. It fails earlier.

This is usually caused because the .INI file doesn't correctly reference each network.

netInternet=VM Network

netManagementNetwork=VM Network

netBackendNetwork=VM Network

I've seen this error if there are bad characters on the network name lines. e/g/ spaces or tab characters after the names. Check these very carefully. Perhaps use NotePad++ to see if there are any bad characters in these lines. Alternatively send me (by private message) your .INI file, and I'll let you know what is wrong. Look at the sample .INI files supplied, because we know all of those work.

Let us know what it was.