I found out myself.
I created a backup of the file Beo5CT.exe.config and edited all lines that were referring to the firmware version to a non-existent value.
Example:
old entry: <add key="Beo5RevD.bin" value="1.41a" />
old entry: <add key="Beo5RevD.bin" value="1.47a" />
I then downloaded the configuration to the Beo 5 - as the version of the firmware in the config file was higher than the one residing on the Beo 5, it copied the files to the Beo 5 without complaining.
After that, the Beo 5 did no longer work. Instead, it showed on its display that the configuration was invalid.
I then modified the entries back to the original firmware version and copied the configuration again. This time, the older firmware version 1.41a was written to the Beo 5, and everything works fine.