Probably a bad relay switch on the motor.When they go bad they can stop working totally and then miraculously start again at any time. Mine froze one night and just about ended my relationship with my car. Anyway, I would just tap the relay with a screwdriver and it would start agian. Kind of makes you wary about reliability and safety of the Powermaster system. Only two choices in my book. Vacuum brakes or Hydroboost. Vacuum works for most and is the cheapest way to go. I chose Hydroboost and am lovin it. More expensive, but reliable. NO more Powermaster BS.
