Turns out the problem was relatively simple to fix. Turns out Magnolia (Best Buy) did not send the processor back to McIntosh for repair, they sent it to their own repair center. Here they loaded the processor firmware but not the USB audio firmware! As I thought, the USB port was effectively not there. After another 3 weeks I now have the pre-amp/processor working perfectly with fully update firmware (Processor and USB audio).
A special thanks goes out to Ron at McIntosh who was very helpful identifying the problem; even though McIntosh had nothing to do with creating the problem in the first place.
A special thanks goes out to Ron at McIntosh who was very helpful identifying the problem; even though McIntosh had nothing to do with creating the problem in the first place.