Here is file that you need for repair:
[Only registered and activated users can see links. ]
Instal usb drivers from Garmin website
flash in preboot with folder Cure and you will have mass storage access
remove gmapprom.img and then flash in preboot with folder original.
If all go OK your nuvi now work.
I am voluntary fireman and in Slovenia we have emergency conditions and i dont have time so if anybody can asist if he have more question.
Here you can see what i talking about [Only registered and activated users can see links. ]