Word doesn't recognize existing citations


I am working on a very long document in Word 2010.  Multiple sections, bibliographies for each section, hundreds of references.  Now, Word doesn’t seem to recognize the existing citations.  They are not editable, they don’t show up in the reference list. The existing bibliographies won’t update.  Adding new citations starts at #1 and Word tries to create a new bibliography.  Converting to unformatted citations doesn’t change the existing ones at all.  If anyone has a suggestion, I would be very grateful.  I do not have time (nor likely the heart) to redo all 500+ references in the text.

I have dozens of previous versions.  I don’t know when this problem started, but it is present in at least the last 10 versions.