I use a WD My Passport for Mac for Time Machine backup, and I had it plugged into my Macbook all day. No problems when I disconnected it. But when I plugged it back in and entered my password and click "unlock", nothing happens but the password window gets greyed-out and hangs, unless I remove the drive cable from the Macbook. After rebooting the MacBook, I still see the Time Machine error icon at the top of the screen (! within the circle). How can I get past this? Why is this happening? Very frustrated... The Time Machine error is "Backup disk not available", probably because the password box is still open even though I'm typing the correct password.