title: Can't check checkboxes on second attempt
body: <p>I can't check checkboxes on second attempt(i can check then uncheck, but after this no effect)</p>
  
  <p>See <a href="http://jsfiddle.net/SM5qU/1/" rel="nofollow">http://jsfiddle.net/SM5qU/1/</a></p>
  
  <p>Attributes set to checked="checked" but no visual effect.
  I am using MacOS and tested in Chrome and Firefox</p>
  
  <p><strong>HTML</strong></p>
  
  <pre><code>&lt;input type="checkbox" /&gt;
  &lt;input type="checkbox" /&gt;
  &lt;input type="checkbox" /&gt;
  &lt;input type="checkbox" /&gt;
  &lt;input type="checkbox" /&gt;
  
  &lt;button id="check"&gt;Check&lt;/button&gt;
  &lt;button id="uncheck"&gt;Uncheck&lt;/button&gt;
  </code></pre>
  
  <p><strong>JS</strong></p>
  
  <pre><code>$('#check').click(function() {
      $(':checkbox').attr('checked', true)
  })
  
  $('#uncheck').click(function() {
      $(':checkbox').attr('checked', false)
  })
  </code></pre>