HI
I am having a problem with my nuvi 255
I am unable to uncheck CN MAP when I want to access other maps on sd card.
I was able to but not now ?.
I have done a reset ,screen calabration updated the software ect ...I know how to manage the maps through mp info screen.
My only thinking is that a file has been deleted bfore I ve backed it up
The maps I have on the sd card are able to be unchecked,but the CN MAP OVERIDES THEM
Try uploading the maps you have on the SD card to a new SD card. Perhaps there is something "hung up" or otherwise affecting how files & programs are being read on your current SD card.