Sims 3: Loading household error?

Hi, thanks for clicking! Anyway on a few of my households, when I try to load them, an error message pops up and says that a serious error occurred and I should restart the program yada yada yada. The thing is I spent ages and ages on a sims 3 household, and really want that save back. It was really the only one I worked on. So how do I get it back. I tried renaming the backup file, but it didnt seem to work, unless I did it wrong :S Any help? :D