I have a MacBook Air running OSX 10.8.4 and a G Drive Mini external USB drive that I connect a couple of times a week for Time Machine backups. I recently turned FileVault on for both the Air and the external drive. Before I did that I could eject the external drive and immediately unplug it. If I listened closely I could hear the drive stop spinning immediately after I ejected it. After turning FileVault on when I eject the drive it continues to spin and if I unplug it I hear a nasty sounding click coming from the external drive. I finally found that if I eject the drive and wait about 7 minutes it will finally stop spinning and I can unplug it without it making the click. I'm assuming that the click is a bad sign and that the drive shouldn't be unplugged while it is still spinning. There isn't any visual indication -- as soon as I click the eject button the drive disappears and would seem to be safe to unplug. I've done a lot of searching online and couldn't find anyone reporting anything similar. I'm assuming this is related to FileVault but recognize that it could be something else happening and just coincidental that it started when I turned FileVault on.