Thanks Götz for a characteristically fast and empathetic reply! 
Yes, this was with the brand new 3009 build, though I have no reason to think that has anything to do with it.
As you guessed, I did try a few variants, and did hit on settings that worked…
Interesting, I was able to export the meshes only when vertex normals were ON and camera export OFF. If I reverse the two (normals OFF, cameras ON), the export fails.
Very strange!
Anyhow, for the moment I’m fine and I thank you again for checking in. I hope the discussion board begins to heat up again in the near future to make it more interesting for you…