According to a Federal Aviation Administration (FAA) inspector, the airplane had just returned from a training flight and the engine was still warm. The pilot told the inspector that she had difficulty starting the engine and opened the throttle "just a bit." She said she set the parking brake and her feet were on the brakes. The engine started and went to high rpm. The airplane lurched forward and collided with the fixed base operator building. The FAA inspector said he examined and tested the brake system and found no anomalies.