That happens in my wife's Olds Intrigue. When backing out, I gently have my foot on the brake and all of a sudden, the brake "boost" up, and the car comes to an abrupt stop. The first time that happened, I thought I hit a cat or dog....
98 GL sport (V6 MTX)
The Durable Duratec? - (DMD, Metal impeller WaterPump, Synth & Stinky in the tranny)