I would try pulling the fuse to the navigation or unpluging it and leaving it out for 20-30 minutes and reinstall. That should reboot the system. They reset procedure for iDrive is hold down dvd and cd and radio off/on buttons at the same time but I don't know if that works on earlier years.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas