I think I have figured out the problem. I discovered that what the display shows when playing MP3 CDs is the file name, not the ID tag information.*So because my car was built on 28.2.2005 and is a very early facelift E65, I suspect the car is not coded for MP3 playback even though the CD changer is able to play MP3s. So the iDrive does not recognize the ID3 tags.
I need to find out how I can re-code the car.