Using zombie apocalypse, I made a playable into a zombie. When I went to the lot she lived on, she looked like a zombie and made the groaning noises, and had the option to "Eat brains" but she walked like a normal sim.
That's a state-change consistency issue. When a sim suffers a state change on another lot, the sim's state may not fully "reflect" when you return to the lot where it was normal. Give it some time to regain normality.
Basically, I just want to know if I can back up the neighbourhood and then reinstall the whole game, or if I even need to (I'd rather not because that means finding all the discs.)
It is unknown what would cause all those weird errors. Are there any error logs that result?