title: NSTextView : contents are gone when scrolling, and shown when on mouseover
body: <p>So this is my issue :</p>
  
  <p>I've got an an <code>NSTextView</code> with lots of content in it (white foreground on black background, if that matters), residing in a Sheet (triggered with <code>beginSheet:modalForWindow:</code>).</p>
  
  <p>The thing is that, when the I'm scrolling, the contents seem to be hidden.</p>
  
  <p>But, when I'm hovering the mouse over the scrollview/textview, the contents are there again.</p>
  
  <p>So, what's that? Why is that happening? How could I avoid this weird behavior?</p>
  
  <hr>
  
  <p><strong>Screencast :</strong> <a href="http://www.screencast.com/t/Sqrk2mdB" rel="nofollow">http://www.screencast.com/t/Sqrk2mdB</a></p>