Driving approximately 55 - 60 mph on an extremely cold (-20) morning. tried to brake and brake is very hard and does not stop. after pumping the brake several times, it grabs and brakes properly. this is the fourth time this has happened in an approximate 30 day period (all during extreme cold). took car to dealer and they find nothing wrong with the brake system. i have subsequently found the articles about the nhtsa opening an investigation into braking problems on the mazda cx-9 that sound identical to the problem i have been experiencing. *tr