I also have this problem; I work at a University with an staff network so it used to disconnect/connect as I went from building to building, even walking past campus buildings, and then connect to our home network as soon as I parked my car outside the house. Shortly prior to JB update, it wouldn't connect at all except to the University 'guest' network (insecure) although it would still work automatically with our home one, and then since, it will only connect when I tell it to.