I agree it's amusing - Mrs C hadn't appeared in my game at all yet! I think I'd be inclined to remove all my hacks to see if the problem goes away. If it does, then you need to replace them systematically so you can weed out the problem, if the problem remains, well, I suppose you could try your downloads?
Since, if it is downloads causing the problem, you won't want to spoil your nice houses etc., you could make a new neighbourhood just to test in.
However, although I agree it wouldn't be Inge's piano fix thing that's causing the problem in itself, it might be conflicting with something else in your game, so you could remove that first just to see if the problem goes away (that's if you haven't already tried that.)