title: Silverlight 4 application freezes without throwing any exception
body: <p>I'm developing a Silverlight 4 RIA application. There is a <code>DataGrid</code> storing data and two buttons: add a new item and remove an item. After creating a new item for the <strong>second</strong> time the application freezes like <a href="http://2.bp.blogspot.com/-UQMUL1DbZPQ/TuCbRKE3dRI/AAAAAAAAAMU/X-RaZ_2nH5U/s1600/abc.jpg" rel="nofollow">this</a> - I'll explain the strange behaviour below.</p>
  
  <p>The scenario of creating a new item looks like this:</p>
  
  <ol>
  <li>After clicking, the child window appears. The reference to the domain data source used on the parrent page is being
  passed to the child window in the constructor. </li>
  <li>The user chooses a file.</li>
  <li>The file is send to a web service. In response the web service returns some data from that file.</li>
  <li>A new data object is being created and inserted to domain data source.</li>
  </ol>
  
  <p>The child window causes the entire application to freeze only when it's called twice, but the first call requires object creation. I can open and close the child window repeatedly and everything will work fine until a sequence of: open.create -> open.close / open.create occurs. I tried to trace all exceptions with VS tool (alt ctrl e) but there are none.</p>
  
  <p>A breakpoint on</p>
  
  <pre><code>private void Application_UnhandledException(object sender, ApplicationUnhandledExceptionEventArgs e)
  </code></pre>
  
  <p>does not show anything either. Any ideas?</p>
  
  <p><a href="http://pastebin.com/RRSvbwiv" rel="nofollow">Page code.</a>
  <a href="http://pastebin.com/uEJvn6B2" rel="nofollow">Child window code</a></p>