Uninstalled everything. Reinstalled version 11.48 you gave me, Borate. I checked out the video you uploaded...yep, that's mine (dammit, had the wrong mic again!). When I exported, it failed again, then again when I updated my Lenovo Thinkpad.
When I updated the intel drivers, though, it all worked just like it did before. The noise you heard a while ago was the happy sigh. Intel drivers appeared to be the culprits.
Thank you! I'll pay more attention to my drivers--computer is only a few months old, but obviously something changed.