Thanks for the prompt response, and I tried that, too. ImgBurn still fails, complaining that there is no room on the target media (a standard, single-layer DVD-R MID: MCC 03RG20).
And then I spent %$(#@& minutes dragging the 1989 files to the queue, again, as described in the Guide to Using The Queue, and it failed again.
While I await word of a correction (to my actions) or fix (to ImgBurn - I guess that would be a 'correction', too?), I am constructing queues limited to fit onto single media -- that is, I am doing it by hand.
La'Shonah Tovah - Mort