Well, surprise! I decided to move on, pending any further developments on my Listing problem. I took my full Carrara-rigged, lo-poly, Carrara-morphed, Carrara-everything, models-that-wouldn't-List and placed it in My Objects browser so I could use it in a scene I was creating. I loaded this model into my scene and proceeded to pose it with the skeleton and any morphs I could create on the fly.

And for no good reason except "why not?", I decided to try VWD again.

And... It Listed!!!

Went back to the original model that wouldn't List, and it still won't List. Back to my scene and it still Lists. Yay!

But why the one won't List and the other will, I just can't figure.

And, BTW, it worked wonderfully, even on my messy models.

Now, I need to better learn how to operate VWD and the Carrara Bridge!

Thanks again, Philemot! It's a workaround, I suppose, but at least I got it working. If any other clues appear on this question, I'll post 'em.