title: Ubuntu not fully shutting down on VirtualBox
body: <p>I have installed Ubuntu Precise (v. 12.04) on VirtualBox v. 4.1.12, on two different machines running Mac OS 10.5.8 and 10.6.8, respectively. All works as expected. I can shut down Ubuntu using the "Shut Down" command in the menu, and the guest OS does indeed shut down. </p>
  
  <p>But when I try to shut down from the command line using <code>sudo halt</code>, while the guest OS does shut down, its window never disappears.</p>
  
  <p>Does anyone have any idea why this might be? I have no such problem with Ubuntu Lucid (v. 10.04) in the same environments.</p>