Just updated my mbp to Mavericks, and found this strange bug with using Finder and its new multi-tabs. When there are mutli-tabs of finder and I want separate them by selecting one and dragging it out, it shows a tiny preview of the finder while still holding down the button and releasing it will split the finder into 2 windows, however, the little preview still appears on the desktop background forever until I restart the computer. Also when using 'app expose' those tiny preview boxes also get selected even though I have closed their windows. Clicking on them doesn't do anything either. Restarted after installing mavericks, but problem still persists. Can someone tryout the same thing and see if this happens to you too?