hmm, can't say i've had any problems like that with lots, but the game has crashed a couple of times...
but there was this lot in one of my created neighborhoods that had issues...
must've been something to do with the sheer misfortune of one of my sims, who was killed by a piece of spacejunk or something while gazing at the clouds... (what the?!)
many strange things happened there after that... in the end i deleted the lot.
and in my current family, the parents's double bed recently started only allowing one person to use/sleep in it at a time (this makes it rather difficult for them to woohoo, so now they've got a hot tub!)
but what's more annoying, i'll *never* be able to get rid of this faulty bed because in buy mode it always says "can't select object in use" when there's no-one using the bed and no-one with any intention of using it!
*grrr*