12 mth old stopped talking!?!?

I wouldn't worry unless he starts to act like he doesn't understand you. The same thing happened with my son, but his pediatrician chalked it up to him being so into learning how to walk and getting more into his surroundings, and he was right. He's so young right now, and little boys tend to be more "hands-on" at this age, so I would think it's just a phase, and that he will start talking as soon as it becomes of interest to him.