I had a similar ignition problem where I took the key out but it didn't register that the key was removed.

The solution was to replace the ignition switch as it had a stuck solenoid.

'07 4.2 Q7, Light Silver/Black Leather, 3rd Row Seats, Cold Weather, 4-zone, Panorama Sunroof, AMI, Sirius, Tow Hitch and 19" wheels
'01 allroad, Atlas Gray, 6-spd, RS6 Taillights, 3rd row