title: A box keeps appearing under the cursor
body: <p>I've almost finished my first (and big...) Qt app, and first time using Qt Creator (Qt 5.4.0)  But one problem remains.</p>
  
  <p>When I stop moving my cursor, this thing appears below, within app window </p>
  
  <p><img src="https://i.stack.imgur.com/a3u4Z.png" alt="http://i.imgur.com/zbtij4u.png"></p>
  
  <p>Once it appears, it disappears only when I start moving it again, just to pop-up immediately when I stop.</p>
  
  <p>I have 2k lines of code and none of it is in any way connected to mousepads. What's that? </p>