I presume you have DVD based COMAND, and you are in Europe - if that is not the case, then the disk recomendations are wrong.
Often wrong position is caused by a faulty GPS antenna.
If you've gone back to 4.1 from a newer version of the firmware it may be just confused
Also, early versions were always slightly "behind" in terms of giving directions - you should update really - see items 3 and 4 on this page (depending which car you have)
Comand Online Ltd :: Mercedes SatNav/COMAND :: Mercedes Navigation Disks :: Europe
Richard