When travelling at approximately 75mph in the fast lane on a motorway, my 2006 Audi A6 Allroad diesel lost power. The engine was still turning over but the car was going slower and slower. Despite trying to accelerate, nothing happened. I got to the hard shoulder and turned the engine off. Then it started again, no problem. No warning lights came on. This has happened twice now in a month. The car had a full service in December 09 and a cam belt change then. I would be very grateful for any information you may have on this.