Power Assist Brake problems of the 2001 Volkswagen GTI

I'm the owner of a golf Gti 2 doors from 2001, with 49000 miles, bought in 2004 at the vw dealer in greenville. I've been about 15 times to the dealer for different problems that were all minor. And 10 months ago, I left the car at the garage for 3 days asking them to make a full revision of that car because I was upset by all these problems. Yesterday, I was driving when suddenly and without any previous signs, the brake pedal became very hard, I lost braking, the asr (traction control) signal went on, and I couldn't stop the car. Hopefully for me, I was only at 40 mph, I put the gear shift in neutral (because the car was trying to accelerate), and I pulled the hand brake. I was able to stop on a parking on the side without hitting anybody or any car. I was very lucky not to have panicked. It is a major safety issue and I wrote to vw USA to explain my major concern.