Montana 680 T updated to the latest version of software (version 3.50).
Several .img files on the SD card: A.img, B.img, C.img etc
The Montana will display files A.img and B.img but not C.img.
I move the file C.img from the SD card to the Montana internal memory and the map displays fine.
Since it has been moved it is the exact same file and the other .img files on the SD card work fine
Any suggestions as to why the file needs to be in internal memory rather than the SD card?