Been scouring the internet and haven't found any explanation, so hopefully someone here has one. On both my Macbook Pro and my iMac I'm seeing a small window showing up in one of my "spaces" in Mission Control. In the attached screenshot it shows in Desktop 1, but before I restarted it was showing in Desktop 3. I have no applications running and can't determine what it might be. Clicking on it does nothing, and being in the Desktop it's showing in and opening Mission Control doesn't bring anything up. I tried to search through the Activity Monitor for anything that might be running out of the ordinary, but don't see anything. Does anyone else have this mysterious window? Or any way to know what it is since clicking on it doesn't open into anything? It's not anything visible anywhere except Mission Control, and when any other program is open (Safari, iTunes, etc) it still shows up on top of them in the Desktop preview. It's driving me crazy. Any thoughts?