- Use save as and a new name instead of save
- Try saving in Edit Town mode as well as live mode
- Try saving your game paused and unpaused and at different speed levels.
- Move your saves folder to the desktop
- Never use save & quit. Always save your game first and then quit the game without saving.
- Don’t use spaces or special chars in your save game names.
- If you have lots of stuff in your inventory, reduce it.
- If all fails, quit your game without saving and restore a backup.

credit: http://sims3.crinrict.com/en/2011/03/error-save-errors-error-12-13-or-16.html