title: Cannot upload Ipython Notebook by drag and drop into DashBoard
body: <p>I downloaded the tarball from <a href="http://jakevdp.github.com/mpl_tutorial/_downloads/notebooks.tgz" rel="nofollow">this site</a>.  I selected all the notebooks in one directory and dragged them over to the IPython Notebook Dash. All of them appeared with an upload button and renaming options. So far so good.<br>
  Then this weird behaviour started. Only the files with .v2 in the filename (full name : filename.v2.ipynb) were successfully uploaded.<br>
  <a href="http://i.stack.imgur.com/PFObf.png" rel="nofollow">Screenshot of Chromium Browser</a>  </p>
  
  <p>System:
  Ubuntu 12.04 (23.0.1271.97-0ubuntu0.12.04.1)
  Chromium Version 23.0.1271.97 </p>
  
  <p>I tried the following already:<br>
   1. added .v1 to the filename<br>
   2. renamed the file completely to a random string<br>
   3. couldn't reproduce the error with other notebooks</p>