Well I'll be
I did the whole run-through on another install just so I could tell you what the error message was, and it worked fine. I don't know what happened before, but it was quite ornery about accepting my upgrade. "internal error" i believe, with nothing in the logs.
Note, however, that mine is a special case, as I had to migrate my install to a new machine to upgrade it as the old one is a dinosaur that is vital enough that I can't afford to restart it long enough for a full OS update but whose OS is ancient enough not to support any modern version of php or mysql.
Anyway, thanks for the advice; the check box to manage FAQs worked fine. Perhaps it should be enabled by default for administrators? (I don't know if it is for most people and i'm a rare case).