title: jquery data() method does not work in IE9
body: <p>I have the following link:</p>
  
  <pre><code>&lt;a href="/Packages/PackageActionDownloadAsync" data-ajax-type="Download" data-ajax-packageid="AGI-VS-GAME-M52-1.5.3.2.67" data-ajax-machineid="30" class="iconGear action tip" data-hasqtip="true" oldtitle="Download" title="" aria-describedby="qtip-1"&gt;Download&lt;/a&gt;
  </code></pre>
  
  <p>and javascript code:</p>
  
  <pre><code>       var obj = $(this),
              objData = obj.data(),
              packageId = objData.ajaxPackageid,
              operation = objData.ajaxType;
  </code></pre>
  
  <p>I tried this:</p>
  
  <pre><code>alert(objData.ajaxPackageid);
  alert(objData.ajaxPackageId);
  alert(objData.AjaxPackageId);
  </code></pre>
  
  <p>they all return "undefined". The only one that works is this:</p>
  
  <pre><code>alert(objData.ajaxType);
  </code></pre>
  
  <p>what is going on?
  I'm using <strong>"jquery-1.7.1.js"</strong></p>