Objects in house disappearing when roof is up

I'm having a bit of an odd glitch in my Sims 3 game. Whenever I click on the 'Go up a Floor' button and reach the top level, the roof, the items inside of my house suddenly turn invisible. I can see through the windows that they're gone, but as soon as I drop back down a couple floors, they reappear. 

It's incredibley strange. Nothing gets deleted, I can go back down the levels of my house and everything will always be in its place with its custom palettes. Animations don't stop, and you can still see sims through the windows, it just looks like they're ineracting with thin air. Unfortunately, I don't know what I might have installed that is causing this problem. I noticed it a couple days ago, but I might have had it for a lot longer. I don't typically play with my roof up.

Having this glitch isn't the end of the world, but I would love to know if there's a common fix.