That is an error listing the files in the device storage. This has been known to happen with some
devices when they contain SD cards. If you remove the SD card, you should be fine. You can try reformatting the card
or using a different card as well. If there isnt an SD card then your remaining options are a reset of the device or using one of the wireless file transfer methods described here:
https://manual.calibre-ebook.com/faq...kindle-fire-hd