On Thu, 8 Feb 2018, Cris Fuhrman wrote:
2. Copy all the entries from the existing "biblatex" library and paste them in the library created above.
Cris, This was not necessary but you pointed me to the problem ... now fixed. Thanks very much! The one place I did not check was the jabrefdb.bib file. Opening that in emacs I saw that the problem Helsel references had an entry for 'journaltitle' (the biblatex syntax), but other @Article entries displayed the bibtex syntax of 'journal'. So, a quick global search-and-replace set all @Article entries to 'journal,' 65 out of 620 entries of that type. Closed JabRef, re-opened it, processed the three Helsel citations from JabRef to LyX et voila! All's well once again. How these 65 records were changed shall probably always remain a mystery. But, it's a good lesson learned so I can fix the problem should it ever arise again. My thanks to all of you: Scott, Juergen, Paul, and Cris. Best regards, Rich