title: Emacs startup warning
body: <p>I am using Emacs for Mac OS X 24.2. 
  Once the emacs was stuck and then I kill the process, but when I reopened it, some warnings were showed below：</p>
  
  <pre><code>warning: desktop file appears to be in use by PID 200.
  Using it may cause conflicts. Use it anyway? (y or n)
  </code></pre>
  
  <p>From then on the message shows every time when I open Emacs, so what we should do to fix it? I am really annoyed for that.
  By the way, my os is Mac OS X 10.7.5</p>