I wonder if this could be a Mavericks issue? OP are you running Mavericks (OS 10.9) on your Mac. That is what I'm running on mine. I don't have a Kindle at the moment so I cannot test. I have never encountered that issue with ejecting a Kindle or other devices. It could be there is another Kindle driver issue with Mavericks, or Mac OS X in general. I would definitely call Amazon's Kindle Support.