Well, I cranked up the laptop this morning, and it all works beautifully.
I'd previously done a shutdown and restart, and nothing had changed, the problem was still there.
I guess all the electrons in Chrome just needed a little sleep, and some time out to think about what they were doing, and to re-arrange themselves.
Then again, it's entirely possible some IT operative within Google spotted my complaint, and thought, "Oh $h*t!! - I know what I did wrong yesterday, I'd better fix it fast!".
