Well, turns out the garage guy who installed my chains did so improperly. The inside end of the chain became loose and severed my brake line. Now i have no power brakes and I'm stuck in South Lake Tahoe with my wife and kid. All garages, shops, etc are closed since it's Christmas and I can't get it towed to the nearest BMW shop until Mon/Tues. Looks like I'll have to find a car rental tomorrow to get home and leave the X5 with the towing guy until next week...