Hi
First step would be that as long as no other errors are cropping up, it sounds like the sensor in the ignition is acting up, it keeps detecting the key even after the key is removed.
Have a look at RangeRovers.net under repair and alarm diagnosis, there is a section on False Ignition Key In which might well hold an answer for you.
I hope this helps
PS Rangerovers.net is a superb site for us RR owners
cheers
Adam