I just starting having this problem with one of my Macs. I have never seen anything like it. A quick Google search didn't come back with anything other than the VoiceOver trick, which didn't work. Essentially, there is this folder in the middle of my screen. If you click the red button, nothing happens. If you minimize it, another folder is created, and that goes down into the dock. The green button has the effect shown in the photos. If you drag the folder, another one pops out, and the original one stays locked in place. Any ideas on how to get rid of this folder, with the black outline? I have tried the logging in and out, relaunching the finder, and restarting.