Definitely a “contact SanDisk for a warranty replacement” issue. But, since you seem to be the adventurous sort, you might first try reapplying the firmware and see if that works–it can become corrupted.
Definitely a “contact SanDisk for a warranty replacement” issue. But, since you seem to be the adventurous sort, you might first try reapplying the firmware and see if that works–it can become corrupted.