Re: Error Code 12

if your playing at the moment save and quit or just quit check to see  if there are any files in your the electronics arts/thesims3/CurrentGame.sims3 that folder should be empty too if there are files in there delete them...while a game is playing  files will be there that is normal but once we save and quit the folder empties out also if you have any save games in the saves folder that have .bad at the end of the save name delete them they are no good

an FAQ on save error codes http://answers.ea.com/t5/The-Sims-3/FAQ-Save-Errors-Error-12-13-15-16/m-p/652/message-uid/652#U652