One last try: I jumped to the quite possibly erroneous conclusion that zapping PRAM was the solution and tried to clarify earlier...apparently unsuccessfully, so...
I zapped PRAM with the applicable boxes unchecked, and initially overlooked the possibility that it was simply the restart with the boxes unchecked, not the zap, that cleared up the issue.
Since I can't recreate the issue I can't test, but I'm inclined to agree with V1 about zapping PRAM, and I now think that the restart with the boxes unchecked, not the zap, was the answer.
