Originally Posted by geoffwood
Make sure you are properly "ejecting" the card before you disconnect it from your PC. Failure to do that can easily corrupt an SD card or USB Drive.
Yes, I'm careful to eject the device from Calibre, then check to make sure it's still not listed under Windows as still being a hard drive before I unplug.
I've also remembered to go in and have my anti-virus not scan the reader and card drives. Just in case that was mucking things up in the background.