Loud screeching noise from MMI in A5 Cabriolet 2011

Newbie Joined: Nov 30, 2012 Posts: 1

I turned on the engine of my Audi A5 convertable (2011) and heard a noise equivalent to a concorde jetplane taking off, i was certain the world had come to an end, frightened and lost hearing in my left ear temporarily (still not hearing 100%) had to call out the Breakdown service as it wouldn't go away. I had to use ear defender when i insert the key in the car next, this went on for half hour or more.
By the time the Breakdown people came it was not happening anymore, but its been a month now and today the sound in the Multimedia stop working, no sound in Radio, SATNAV, IPod, CD everything.
Am i the only person to have this problem with this? Mileage 15,000 so not a lot of milage for the age of the car.