Earlier today I was sat in the car, parked, I pressed the Engine Start/Stop to go into Accessory Mode so that I could listen to the radio. The radio turned on but I noticed that the HDD Navigation System screen was blank, so I pressed the ‘Back’ button. Nothing happened (I would have expected the warning notice to be displayed). I pressed the ‘Menu’ button but still nothing. I pressed the ‘On/Off/Volume’ control and the radio remained on. I pressed it again and the radio stayed on. I tried to adjust the volume but the ‘Volume’ control had no effect. I then tried the ‘Source’, ‘Chanel’ and ‘Volume’ buttons on the steering wheel but there was no response from any of them. I then tried pressing all of the buttons on the HDD Navigation System in turn with no response from any. I turned the Accessory Mode off then back on again and the display remained blank with no response from any controls so I turned Accessory Mode off. I tried to turn the radio on using the ‘On/Off/Volume’ control but the radio would not switch on. I started the engine and everything worked ok. Strange. I have used Accessory Mode many times to listen to the radio while parked and this has never happened before. Has anyone else experienced anything similar?