title: Show and Hide Modal Popup Extender Not working
body: <p>Hi all I have a modal popup extender set to a hidden linkbutton.  So when I want to use it I am doing</p>
  
  <pre><code>protected void ProcessFileBtn_OnClick(object sender, EventArgs e)
  {
      WaitModalPopupExtender.Show();
      //DO STUFF
      WaitModalPopupExtender.Hide();
  }
  </code></pre>
  
  <p>Process takes a while, but no Modal Pop Up extender shows, when I create a button just to do the show function it works, but when I add in this</p>
  
  <pre><code>protected void Test_Click(object sender, EventArgs e)
  {
      WaitModalPopupExtender.Show();
      System.Threading.Thread.Sleep(5000);
      WaitModalPopupExtender.Hide();
  
  }
  </code></pre>
  
  <p>Nothing shows up.  Any thoughts?</p>