Hi there! It's the first time I write here
This is an old topic indeed. Nevertheless, it is still relevant.
Just to confirm:
I sent a ne book with calibre, but after finishing I was unable to umount, so I just unplugged the device, resulting in the well known 1fskin:/l/string screen.
I wasn't able to rename \database\cache\media.xml. Linux said that it was unable to write in the file system and Windows said that the file was corrupt and it wasn't able to rename it.
I felt a little bit risky and just deleted the file. Anyway, the information was already lost!
The good news is all my books are still there. the bad ine is that all my notes and collections are lost
I hope my experience is useful for anybody.
Bye