You folks are amazing!! What creative and intelligent ideas! I tried several of them, with these results:
1) The stethoscope: determined that there are no wood parts loose. Couldn't get a good fix on strings though. Sure made them sound loud!
2) The third fret possibly loose: Ginny thought the same thing, but nope. Nice and tight. However, there is some fret wear on the first and second strings - on the 2nd, 3rd, and 5th frets. Also a little on the sixth string, 3rd fret. This opens lots of possibilities, don't it?
3) Looked for bees. Might be a swarm hiding in the B string :)
4) The bridge saddle shape: the saddle is radiused; the bass end is higher than the treble end; it's pretty low, but not terribly so; it's shaped so the 1st, 2nd, 5th and 6th strings make contact with it furthest from the sound hole, and the 3rd and 4th strings make contact with it closest to the sound hole. But as for the arc in the profile: yes, sort of, for the bass strings; but not really for the high B and E. It's kind of flat for them. Good idea, I'll try shaping a new saddle, thanks for that idea.
5) Pressing between the nut and first frets, and at the point where neck joins body (14th fret): decent amount of curve. We slid some feeler gauges through there and took lots of notes. The biggest gap was at the 7th fret: .015", which I think is slightly low action, but not abnormal?
6) Frets.com: Frank responded to my question, saying he thought it might be a "back buzz" on the low E. He suggested raising the low E in the nut with a piece of paper and then testing. Well, this may be paydirt! With a piece of paper in there, the buzz characteristic changed to a quieter buzz that ends abruptly. And if I leave the paper in there AND damp the low E anywhere between the nut and the 3rd fret, the buzz is GONE. I wrote these results back to Frank, and he suggests maybe raising the nut a bit, or loosening the truss rod even a little more.

THANKS EVERYONE, BY JOVE, I THINK WE'VE GOT IT!!! GINNY AND I ARE ONCE AGAIN HAPPY CAMPERS.

Bark Woof