Some microSD and (much more rarely) some SD cards will not allow the 'BOOTDISK' signature to be written to the first sector
That would explain the behaviour i.e. the new dryos is actually working but it is not booting properly.
Unfortunately the camera was a present so I have only got a 8GB real SD Card (and no card readers - i.e. I use the camera itself to access this SD Card). Instead I have 3 different microSD cards (1GB, 2GB and 8GB) which I can access directly with the computer.
I guess I will need to buy a small SD Card and a card reader in order to give the OS dumping another shot.