"Copy" window won't close

"Copy" window won't close. I was copying my Aperture library to my external hard drive and got a warning that it couldn't be completed. Now the "Copy" window won't close. What controls this, Finder? and How do I close the window?

Also, when I try to open the Aperture library i was trying to copy, the message i get is "Waiting for Time Machine to finish backing up Library" I wasn't using Time Machine. What is going on?