Wondering if you can provide some insight regarding what happened? I have a MKIII and MKIV and have updated both a "few" times. I do recall updating the MKIV the first time and getting a blank screen (panic) and trying it again afterwards successfully. I never did figure out why I got the blank screen but when I shut off the car, disconnected battery then connected battery and attempted again it worked. I always heard of sometimes issues with the MKIII NAV units but not so much with the MKIV units. I did do the update so that I could read the hi density disks.

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E83 - Aero PKG Mods installed: Homelink mirror. CIS-IBUS video module, AUX, Rr Dr Release, stock wheels, Remote start, CarPC (Atom) & mud flaps - NAV - MKIV - NA Map DVD - 2011
E46 - 18.5 wheels/tires (summer), 17 stock (winter), Homelink, NAV software upgrade, BMW video module, Radio to V53, AUX, USB IBUS interface,BMW alarm install, CarPC(Epia), remote starter, tank battery & angel eyes. NAV - MKIII - NA Map CD - High Version 2008.1