I tried all the same things that you did, with the same results. The problem occurred first with an INTEGRAL NEON 32 GB flash drive, ( 6 months old ) after 3 days trying all the problem solving methods I could find I threw it into the back of a drawer. I then put in an IBoutique 64 GB flash drive ( New ) on which I had backed up my photos and music, this is the first time that I had put the 64 GB flash drive into my laptop since backing up the photos and music files. Guess what, DISC IS WRITE PROTECTED. I didn't want to muck about with the 64 GB disc in case I lost the files, so I took it out and put in an PNY8 GB flash drive that had been lying about for a few years, and it worked perfectly. I can believe that 1 disc would fail but not 2 in he same time period especially when 1 is new and 1 6 months old. So I have ordered a new flash drive, and if this one does the same I think I will be going back to putting everything on DVD.
Andy50