Well, that it usually means that the main sector got corrupted, and that still there's a hope that the backup is still alive, but I have never tried that.

You should do what michaaaa62 just said. Make a image copy, of all your internal drive, (first command) then copy the backup cluster (6) to the main (0) (second commnad) and hope for the best |:/

@Michaaa62:
Are you sure that you are copying the sec 6 to the 0 with this command? Shouldn't I try to copy to the sec 6 somewhere else and then try to copy it to sec 0? I don't know much, but looks like you are copying the 6 to the 6 again, am I wrong?

EDIT:I was wrong. I got it!