Geo and others.
After picking my car up from the dealer yesterday (when they said that they could not duplicate the problem, but they checked every wire and connection, and voltages, etc) the sound worked perfectly on the way home. I even took a bumpier road, tried different speeds, hit the HK button on and off several times, and took the dog for an extra long ride. Still no problems, sounded absolutely perfect and beautiful for the first time.
According to the dealer, the very first thing they did was go through and check every connection, unplug and replug, and check the voltages. Then they took the car for a ride around the parking lot, on the highway, and still back and forth. When driving, they had no problems. And when I picked it up...no problems. So maybe in the process of checking every connector, they actually fixed the problem without knowing what it was.
I will update again this morning after driving to work. I would also suggest that you take yours to the dealer and have them do the same thing. At least if we take them to the dealer, then there is a log of what is happening and our complaints are uniform. Writing a letter to BMWNA without even taking it to the dealer will be ineffective as they will just say to take it to the dealer and then write them.