by Doug Smith.
With Ken Task's help, it looks like we found the problem.
I think the mbz backup file I was using had been improperly archived. On my desktop the file would un-archive ok. However, it looks like when it was on my server and with my particular combination of php and moodle server, the file would not un-archive.
Un-archiving it on a desktop and then re-archiving it making sure it was in a gzip format fixed the problem.