when you press F3 objects display/don't display. You cannot select them by clicking then; but you CAN select them by holding down and drawing to select multiple objects. This seems like a bug; in any case I consider this a bug: when I use the F3 option I DON'T want any objects being selected.
now I see that in fact if you press F2 and turn off terrain you can now NOT select anything, even objects if they are being displayed. Again, this only applies to holding down, not clicking singly.
Thanks. This was a copy-paste error on my side: I checked twice whether terrain pieces are displayed, and never whether objects are displayed. :-[