I was able to send the document to Google Docs (sorry but this is not an offer to write how to use Google Docs or where Google Docs is.)
I loaded the failed document in Google Docs and there it was. In Google Docs I was then able to save it as another simple name and get it back.
Word 'encountered a problem and had to close' leaving me with only a much earlier version of my current doc. I can recover the latest version in Textedit, but how can I save it and send it to my publisher? Word is still saying name or path is invalid. NB I am an aged lady so please keep it simple!