Burglars never appear (Sims Legacy)

Burglars don't seem to be working in this version of the game. I'll often hear the audio sting at night, but no one appears (sometimes it's the raccoon of course but other time it's nothing at all). A few times when I've been able to see the edge of the lot, I've seen the burglar appear for a moment after the sting plays, but he immediately disappears while still at the edge of the lot.