C6 Clutch Master Cylinder Failure

I have a 2005 C6 Convertible purchased new and now has just under 20K miles. Just had an almost catastophic failure of the clutch master cylinder. I had just shifted into reverse and started backing out of a parking spot when the car suddenly accelerated, clipping one car and careening down a street at what seemed to  me to be 30-40 mph. I was fortunately able to bring the car to a stop by depressing the brake pedal with both my feet, one on top of the other. There was serious damage to my drivers side rear quarter panel, but thankfully no one was hurt. Has anyone out there heard of or experienced anything like this? I'm thinking that something computer-related was triggered, but I may have a problem getting someone from the dealer to get an expert to examine the "Black box" to
get a record of the sequence of events. I am very apprehensive about keeping the car without getting to the bottom of this. Any help and/or advice would be appreciated.