Server issues
I fear, that if you've started a new springfield whilst logged into your origin you cant get your old one back.
Forum Discussion
Had same problem yesturday (15/04/2013) use a file manager and delete your saved game but make a backup before you do this.
Internal memory\Android\data\com.ea.game.simpsons4_na\files\save
Kill tapped out and then re start it you should be able to log back in with your old town.
Internal memory\Android\data\com.ea.game.simpsons4_na\files\save
Kill tapped out and then re start it you should be able to log back in with your old town.
