title: Invalid file name error in eclipse for images
body: <p>I'm facing the following error:</p>
  
  <pre><code>res/drawable-hdpi/Twitter.png: Invalid file name: must contain only [a-z0-9_.]
  </code></pre>
  
  <p>Twitter.png looks like a valid filename to me. None of the other images having names like Facebook.png, RSS.png work. </p>
  
  <p>Help please!!</p>