I have an external USB 3.0 WD MyPassport plugged into my retina MacBook Pro, and when I go to eject it, I get the following message: 'The disk INSERT DRIVE NAME wasnt ejected because one or more programs may be using it.' I have closed all applications, and have gone into Activity Monitor to see if anything is going on. I've turned off Time Machine and removed the drive from the Spotlight index. The drive is sometimes spun all the way down and I still cannot eject it without a force eject. Any ideas?