I have tried to open the dng images with some linux applications from ubuntu repositories.
Ufraw crashes on any dmg.
Rawstudio shows a blurred, red image of something and can't convert it in anything useful with any button or control.

Can you suggest me the right tool? Thanks

EDIT: no image tool on ubuntu repos could open those files. Neither gimp, which outputs some interesting messages:

/home/debernardis/Immagini/photo2010.06.24_15.00.19.10.dng: Can not read TIFF directory count

/home/debernardis/Immagini/photo2010.06.24_15.00.19.10.dng: Failed to read directory at offset 0

before stating that the rawphoto plugin can't open the image.