[CD] Cats can't use the litter boxes

I'm also having this problem on Mac.  I've made sure the litter box is in a clear location, even with the move objects cheat on, and I've reset the litter box and the cat using the shift-left click option.  It fixed it once, but every time I close and open the game it's dysfunctional again.

I've noticed that cats can't find the litter box if it's on a different floor or the other side of the lot. So instead of resetting them or the box when they say they want a clean litter box, I just have one of my sims stand next to the box and call them (or even pick them up and carry them over). Leave them alone right next to the box, and they generally figure it out on their own - at least if they're in the household. Strays can sometimes be more problematic.