My c6 automatic stalled today

[Teekay]

Hi guys, 

I have a beautiful a6 c6 Le Mans 2010 2.0tdi automatic. I have had the car for about 9 months now, had the cam belt changed when I brought the car as their was no service history, I also had the discs and pads replaced and had the big service done. Today, when I started the car and when I tried to do a 3 point turn, as soon as I put it in reverse, the car stalled and switched off, this is the first time my car has stalled. Also, when I was reversing on a hill, i realised that if I don't give any throttle, the car was sliding down the hill, again this has not happen before. Since I have had the car, the gear change is really smooth but in reverse there is a very slight delay. Any advice guys...