Thank you very much Lazer and jojo!
I have used a live gentoo and checked the hardware (SMART) and it is seems in good shape and the issue is probably the filesystem but unfortunately nothing that fsck can repair. Regarding the usb key, it has few broken sectors therefore I would try to recover it using the jojo backup. As you said, it is an old platform but if in a few hours I will repair it it can be useful again ;-)