Transfer Case problems of the 2004 Volvo XC90

I am experiencing continuing safety problems with my Volvo Xc90. This vehicles all wheel drive (awd) system is malfunctioning without warning and at random times. This results in unpredictable and erratic vehicle handling which creates serious safety issues to the vehicles driver and occupants. This has been occurring for at least one year and was confirmed and documented by a Volvo dealer during the summer of 2005. I must point out this safety problem involves an active system that cannot be controlled, adjusted or disabled by the vehicles driver. This safety problem caused an accident during the winter of 2005. At that time, the all wheel drive system failed suddenly and without warning on a snow covered road. This caused sudden and uncontrolled front wheel spin which led to a loss of vehicle control and with the vehicle sliding off a road. A tow truck was required to move the vehicle back on the road. The Volvo dealer that confirmed the problem has made several failed attempts to repair it. They have documented communication problems within the vehicles high speed network and reloaded vehicle software. They have also replaced: 1) the vehicles front wheel sensors, 2) the mfi module used for vehicle diagnostics, 3) the bcm module used by the awd system, and 4) the awd aoc unit with clutch and transmission. None of this has resolved the safety problems I am experiencing from this vehicle. This Volvo dealer has told me the problem cannot be repaired because: 1) the vehicles diagnostic system does not report any diagnostic codes, 2) their own technicians cannot diagnose the problem, and 3) Volvo technicians cannot determine the problem. My requests to Volvo cars of north America have been ignored or rejected, even by Volvo consumer affairs and Volvo regional managers. I am left to driving a vehicle with obvious safety problems that cannot be diagnosed or repaired by anyone.