title: R readHTMLTable failed to load external entity
body: <p>When I run the line on my laptop, </p>
  
  <pre><code>table500 &lt;- readHTMLTable('http://en.wikipedia.org/wiki/List_of_S%26P_500_companies')[[1]]
  </code></pre>
  
  <p>it gets the data. When I run it on my desktop, I receive the error </p>
  
  <pre><code>Error: failed to load external entity "http://en.wikipedia.org/wiki/List_of_S%26P_500_companies".
  </code></pre>
  
  <p>So I'm guessing the problem has something to do with network settings in my desktop, I haven't the slightest idea what it could be though. Any suggestions?</p>