I've been doing a bit of research, but come up with zilch I'm afraid - usually, pears with brown inside have extensive browning, or a tunnel, and the outside of the fruit looks scabby or marked, so I've no clue as to what the problem might be. And apparently, neither has anyone else, as they've not answered you, sorry.

Thanks for trying anyway, Bamboo. We had a look on the net as well, and lots of comments said that pears are best picked slightly unripe, and ripened off the tree, and that if they're left on too long, they'll spoil because they ripen from the inside! We went away for a few days, and when we came back, lots of the pears had fallen off, presumably because they were over-ripe, and most of these were brown in the centre. We took the rest of them off the trees, ansd put them all in a bowl together at room temperature, and they've mostly been fine. SO, we may both have learned something! Thanks again....Annie