Hi, I have a 2007 x5, 3.0. It currently has 66246

sounds like a short in the body can (K-CAN), all the systems you mention including cluster, audio and immobiliser are on it. check first in the boot in the rear corners for water, there are control units and plugs in this area and any water ingress can corrode them and cause this sort of issue

Ok this one could get complicated in a hurry. My suggestion is take it to BMW but I know how expensive that can be. Couple quick questions have you had any work done recently? Are either of the front floors wet? When this failure while driving occured did the wipers start going and not shut off? It sounds to me like you might be having a module failure for the JBE (junction box electronics) I have seen alot of water damage to these modules in the X5 due to blocked sunroof drains in the A pillars. The JBE controls many functions in the vehicle including locks, power supply to many modules and like luke said it is the master module for the body can (k-CAN). The service light is on warning you there is a know issue with your vehicle and should have the codes checked out. Now these codes will not show up with you basic OBD2 code reader you would actually need BMW to scan for codes. Also look at your check control messages in you idrive to see if it says anything about the warning light. Hope this helps let me know on the questions above maybe I can point you in the right direction.