This happened to me yesterday on my new H2o Edition 2 using Calibre on Windows 10. H2o 2 is on the latest firmware.
I normally don't use Calibre so it was the first time I had ever tried using it with the H2o 2 (I was trying to fix
this). I tried a couple of times and Calibre hung, and when I checked the jobs it was unable to get the list of books. It was also not possible to cancel this. It would give an error if you left it long enough, though I did force close Calibre when it first happened.
I had loads of trouble with explorer.exe afterwards when trying to eject the H2o 2. It was hanging and eventually I had to use Task Manager to try and close explorer.exe and start a new process.
Windows showed the 'problem with drive' error when the H2o 2 was next connected so I did a factory reset and thought I'd try Calibre again. Same thing happened. It was unable to read the list of books and Windows started giving the 'problem with drive' error.
When I next got the 'problem with drive' error, I let Windows scan and it said it found an error, but I thought safer to do a second factory reset than let Windows fix.
So I will not be attempting to use Calibre again with the H2o 2 (my old Touch works fine with Calibre). I am able to use Windows to edit the files on the H2o 2 (have done the full screen reading fix) so it seems to me that Calibre is the problem.