OK, I solved this by myself:
in the restoring of the backup, the following entries was set to REG_SZ:
"Common Desktop"="%ALLUSERSPROFILE%\\Escritorio"
"Common Start Menu"="%ALLUSERSPROFILE%\\Menú Inicio"
"Common Startup"="%ALLUSERSPROFILE%\\Menú Inicio\\Programas\\Inicio"
"Common Templates"="%ALLUSERSPROFILE%\\Plantillas"
"Common Favorites"="%ALLUSERSPROFILE%\\Favoritos"
"Common Documents"="%ALLUSERSPROFILE%\\Documentos"
"Common Administrative Tools"="%ALLUSERSPROFILE%\\Menú Inicio\\Programas\\Accesorios\\Herramientas administrativas"
"Common AppData"="%ALLUSERSPROFILE%\\Datos de programa"
@=""
"Common Programs"="%ALLUSERSPROFILE%\\Menú Inicio\\Programas"
I changed them to be REG_EXPAND_SZ (using regedit) and it solved everything!
...don't really know where I read about this on microsoft, but you probably can explain better than me why this should be set this way when there are environments variables in the value...
thanks for everything anyway.
Now I will backup averything (twice!) and try again with the new version...
/j