Thanks to you both!
Tried again
- with updater = On device screen "Loader"
- from SD card = nothing at all
How can I safe the files from the unit for later restore if I cannot get a connection to PC?
Found a solution for my problem - check GarminCure3 tool - the new way to create cure firmwares for Garmin devices
Took me 1 hour to get my nuvi back to work
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