@lumen, @Zeewulf
I also have a 4350Max which I am trying to upgrade to 70 Premium using the procedure outlined at the start of the thread. I have downloaded the update files and the Q1.2018 map/nfs files. Unrar'd the upgrade, formatted the device as FAT32; copied the new files in, along with a few map files and all the nfs files to a new NAVIGON/map directory. Booting up gives me the "NAVIGON software cannot be started" message in English, German and French.

If I connect the device to the PC and use Navigon Fresh software, it recognises the device and says it is running Version 7.7.6 and shows the map files I have installed... it just doesn't boot up

Did either of you (or anyone else) resolve this problem?