Thank you for your reply. I don't consider it a fault, it is merely a setting I can't find. I know some navigation software require to be on the "first" memory card, but I dont know where to change the order of the cards. I suspect a little digging in the registry could reveal the solution, but I don't know where to start...
There is indeed a file telling TomTom which map was used latest, but TomTom "should" search all memory cards for other maps. In my case it only searces the first card (SD). What happens with your TomTom if you move one map (not the one you are using) from the SD card to the CF card. Go into "Switch maps" in TomTom. Will TomTom find the map on the CF card?
Maybe it is time for a hard reset and start from scratch...