It happened to me too. After pressing OK, it redirects me to http://markdotto.github.com/github-buttons/github-btn.html?user=FacialTurd&repo=The-Powder-Toy&type=watch&count=true, a page that doesn't exist. I viewed the html but didn't see anything wrong. What's wrong @Simon?

You can just update from the app or

https://powdertoy.co.uk/Download/powder-win32.zip or

https://powdertoy.co.uk/Download/Browse.html.

And thereis no 82.0(beta)

 <div class="download-buttons">
 <div class="btn-group">
  <a class="btn btn-huge btn-info" href="/Download/powder-win32.zip">
   Download Powder Toy
   <!--<div class="pull-left">Version 81.6 for Windows</div>-->
  </a>
  <button class="btn btn-huge dropdown-toggle" data-toggle="dropdown">
   <span class="caret"></span>
  </button>
  <ul class="dropdown-menu">
 <li class="Download">
   <a>No Beta available</a>
  </li>
  </ul>
 </div>

Oh so it's not just me with the error page? Phew :P