How do I load back that backup file? I'm saving my game under two different names however. Just to be sure. When we're talking about save files I'm just that paranoia as neurotic sims can be.
Ok. So in your Documents folder (or My Documents, if you're on XP)
Electronic Arts/The Sims 3/Saves
There should be a bunch of folders, each ending with '.sims3' Those are your saves. The name of the folder is the name of the save game. You should also see folders ending in '.backup.' Those are your backups. So for each name you should have two folders (if you don't have a '.backup' folder, that's ok, it just means that the game didn't create a backup for some reason, and you're out of luck on this.)
Example: So I've got a save game that I call 'Sunset Valley Legacy.' There are two folders in my Saves Folder. 'Sunset Valley Legacy.sims3' and 'Sunset Valley Legacy.backup.'
So you want to put the folder ending in '.sims3' somewhere like your desktop (so you can put it back just in case this doesn't work), and then rename the folder that ends in '.backup' so that it ends in '.sims3'. You actually do want the entire folder, each folder is a saved game.
Example: 'Sunset Valley Legacy.sims3' gets cut from the 'Saves' folder and pasted to my desktop. 'Sunset Valley Legacy.backup' gets renamed to 'Sunset Valley Legacy.sims3.'
If you see any folders ending in '.bad', that's ok, you can delete those. Those are caused when the game didn't save right for some reason.
Once you go back to the main menu of the game, load the game and see if that works. If something goes horribly wrong, you still have the save file you stuck on your desktop, so you can put that folder back and you will still have your saved game, just when you put it back, delete (or rename) the backup folder first.
Just so you know, depending on how often you save, the game-created backups can be pretty far back.
I hope I explained this well, it's hard to explain via typing.
Hope this helps.
If this doesn't fix it, then you'll probably have to start a new game.