While driving approximately 45 mph towards a stop light. I stepped on the brake and was not slowing down. The pedal went completely to the floor. I pulled the car into the far right lane to avoid smashing into the back of a van. I pulled up on the emergency brake going around a corner praying no one was waiting at the traffic light as I would have hit them head on. The truck gradually slowed to a stop. It was picked up by a tow truck and taken to a BMW dealer.

This was a frightening experience to say the least. There was no warning light, or any idication whatsoever that there was any problem with my brakes.

I'm waiting to hear what the dealer says the problem is. Really hoping this doesn't happen to someone else. I feel lucky, it could have been much worse.

Update from Jul 10, 2013: Update: The BMW dealer replaced the following parts. Hose clamp, 2 vacuum pipes, gasket ring, profile-gasket,seal, brake booster, brake servo unit, brake master cylinder and the circlip.

BMW replaced all of these parts at no charge to me even though my X5 is no longer under warranty.