I also got the Battery Drain warning message today. So you have to eject the NAV DVD to fix the problem and reinsert when you need NAV?
Also the strange thing is picked my X5 on 05/15 (Tuesday) and drove about 25miles on the first day. Then it was idle for the rest of that week. Then I took it for a long drive on 05/19 (Saturday) and a short drive on 05/20 (Sunday). I had NO battery drain message. It has been idle until today (2 days). Now I suddenly get this battery drain message. I am wondering why I didn't get this on Saturday, when my car has been idle for 4days? Looks like this NAV working 24/7 is actually random?