If you have recently put new CC into your game take it out.
This is why my downloads are so organized, I have had this same thing happen almost a hundred times! I always have the folder open that I last extracted content into, this way if it crashes the program or turns the sky orange, I know just what did it. The last time this happened to me it was from the fishing bridge from ReflexSims forum; I was so excited that sims would be able to fish from the pier, alas it borked my game
hard.
I organize everything based on where it is found in the catalog -
1). Game Modifations have the first folder, then sort by who created it.
2). All Neighborhood deco, and items commonly found on Community Lots have the second folder.
3). Build Mode has the third.
So on and so forth. One more thing, many players don't know that you can dump all content for BodyShop/Create a Sim into the SavedSims folder, nothing will be worse for wear. I give defalut replacements their own folder as well, then subdivided by type. I also rar backups of the different folders and store them on a thumb drive, it saves me hedaches.