Thanks for the suggestions, everyone. Oh, and Mark, the ribbon cable doesn't have a scratch on it, but thanks for the suggestion.

It turned out to be pin 2 of the PIC nearest the buttons. I thought I'd touched it up, but it seems not enough. More careful work on pin 2 and all was well. Although Stu, I think you had some of the numbering backwards in terms of which pins needed continuity with which pins on the display connector. In any case, I checked everything, and that was the pin on the PIC that wasn't giving me continuity, so I touched it up and bingo. Thanks again!

Yay! No silent commute for me today!