I recently had this problem, and the number of different system warnings increased every week.
First I spent some money at a general car electrics garage without solving the problem. Then I read all I could find on the net, and became even more confused and worried. Finally I went to the local BMW garage, brought them a couple of prints from different forums and some owners experiences from simular situations, and asked them to check all major cable connections and reset the computer before they started changing any sensors.
That did the trick. It seemed to be one major cable connection close to the gear box that needed cleaning and attention. After resetting the computer all warnings was gone without any further action.
It's now almost three weeks ago, (but still crossing my fingers)