title: Radio Button causing strange behaviour
body: <p>I've got a <code>ModalPopupExtender</code> containing a <code>RadioButtonList</code> which has 2 <code>ListItem</code> buttons.</p>
  
  <p>When the popup is visible, one button is already correctly selected.</p>
  
  <p>If I click the other button, I get <code>Page_Load</code> followed by <code>OnSelectedIndexChanged</code> events as expected.</p>
  
  <p>My Page_Load handler calls <code>ModalPopupExtenderExchangeDevice.Show()</code> which causes the popup to still be visible when the code-behind completes.</p>
  
  <p>The opposite button is now selected, as expected. If I now click the un-selected button, again <code>Page_Load</code> followed by <code>OnSelectedIndexChanged</code> events fire, but this time the <code>ModalPopupExtender</code> is NOT visible.</p>
  
  <p>Any ideas why it isn't?</p>
  
  <p>UPDATE:</p>
  
  <p>Fixed the problem with one RadioButton not working - ASP.NET "helpfully" changes the <code>Request.Form["__EVENTTARGET"]</code> between buttons, and I had missed it. Sorted.</p>
  
  <p>Having fixed that, the popup is still not showing.</p>
  
  <p>Thanks</p>