Sirbruce,
Thank you for the suggestion - I'll update to the most current version and try again.
daffy4u,
Thank you also - I'm well aware that the file does not require conversion to be read. As I mentioned, I need to edit the metadata which reportedly works best if subsequently converted to .mobi before porting to the Kindle. Editing a .prc seems to be ineffective.
(and thank you for the welcome

)