Hello felici.
Try the apps shown on this page: http://forums.sandisk.com/t5/All-SanDisk-USB-Flash-Drives/Download-new-version-lost-access-to-all-data-Please-Help/m-p/301789#M5953 They are completely free.
Be VERY careful downloading random recovery apps you find on the 'net. Most are “free to download” and “free to try” and then charge $39.95, or more, to actually recover your files.
