The big lightbulb over my head finally came on, concerning my particular "problem with plant foods." I took some probiotics this morning.
So as not to provide TOO much information, let us just say that Dr. Donaldson is right about lettuce: "one of the hardest foods to digest that is known."
Gotta get more meat out of the freezer -- i think it's time to defrost the BIG BRISKET. :-D