Strange that my RR MY 2002 has recently developed the same fault within the last few days for no apparent reason. I removed the old 2002 CD and replaced it with a 2009 update that I purchased a few weeks ago but had not got round to fitting. This appeared to cure the problem, the disk stayed put and the sat nav function was restored.
The low battery possible cause is interesting as I've posted previously on the forum the saga of the problems I've had in this respect with my vehicle along with a good many other owners it seems. I've been using my other vehicle for the past few days but when I went to unlock the RR this morning, absolutely no response to pressing the unlock button on the key fob. Unlocked the drivers door using the key where upon the alarm sounded so I immediately thought that the battery drain problems had returned although the vehicle has been performing perfectly for the past few months.
Key in the ignition and turned it expecting no response but the engine fired without hesitation and all the electrics seemed to be OK including the sat nav. Continual rain and damp conditions in Essex for most of the past week so I wonder if the high amount of moisture in the atmosphere could have any bearing?