The creation of the update package was successful. However after installation of the package on the DXG the DXG booted only halfway after which "Your Kindle need repair"-error occured. At the right bottom it said "battery". Maybe it is procedures which are related to the battery which are incompatible since the DXG and Kindle 3 have different batteries.
Anyway, fortunately the recovery console worked and the DXG was put back to life with old 2.5.8 firmware. A software restart was necessary to also get the web browser to work again.
Would it be possible to upgrade firmware 2.5.8 with a smaller subset of v 3.1 e.g. only the webbrowser?