Bernie & Bruno,
Check to make sure that you copied the file 'KN7000MN.INF" when you made backups of your original card. This file resides in the KN7000 folder on the card and it contains the index of what is on the card. Without it your files will not show in the keyboard.
Another hint - the reason that you cannot use Windows explorer to add Technic files to the card is because this index file is not updated. Unless you are really an expert with a hex editer program, the only way this index file gets updated is by either the keyboard when you load and save, or by the special SD Explorer program.
Walt