Louise, my computer, an HP laptop, is running Mint 12. I uploaded Calibre and have stored all of my ebooks in my Calibre library. I regularly attach my Kindle and add books from my library. I have had no problems with my Kindle, to date. My Kindle shows up on my desktop as a mounted drive and it appears in Calibre when I open it. I know this doesn't answer your question as to how to fix the problem, but I wanted to reassure you that Linux os's do cooperate with Kindles.