title: InsertImage in HtmlEditorExtender show blank box
body: <p>HtmlEditorExtender control when trying to upload an image (locally or on server) shows me a blank, does not show me the controls to upload the images, even the button close / cancel</p>
  
  <p><img src="https://i.stack.imgur.com/m8QSX.png" alt="enter image description here"></p>
  
  <p>Environment:
  VS2010 Framework 4.0,
  AjaxToolKit.dll 4.1.7.123,
  HtmlAgilityPack.dll 1.4.0.0,
  SanitizerProviders.dll 1.0.0.0,
  IIS 7</p>
  
  <p><strong>ASP</strong>:</p>
  
  <pre><code>&lt;asp:HtmlEditorExtender ID="HtmlEditorExtender_Nota" runat="server" ClientIDMode="Static"
  TargetControlID="txtNota" DisplaySourceTab="true" OnImageUploadComplete="saveFile" &gt;
      &lt;Toolbar&gt;
          &lt;asp:Undo /&gt;
          &lt;asp:Redo /&gt;
          &lt;asp:HorizontalSeparator /&gt;
  
          &lt;asp:Bold /&gt;
          &lt;asp:Italic /&gt;
          &lt;asp:Underline /&gt;
          &lt;asp:StrikeThrough /&gt;
  
          &lt;asp:HorizontalSeparator /&gt;
          &lt;asp:Subscript /&gt;
          &lt;asp:Superscript /&gt;
  
          &lt;asp:HorizontalSeparator /&gt;
          &lt;asp:JustifyLeft /&gt;
          &lt;asp:JustifyCenter /&gt;
          &lt;asp:JustifyRight /&gt;
          &lt;asp:JustifyFull /&gt;
          &lt;asp:Indent /&gt;
          &lt;asp:Outdent /&gt;
          &lt;asp:InsertHorizontalRule /&gt;
  
          &lt;asp:HorizontalSeparator /&gt;
          &lt;asp:InsertOrderedList /&gt;
          &lt;asp:InsertUnorderedList /&gt;
  
          &lt;asp:HorizontalSeparator /&gt;
          &lt;asp:CreateLink /&gt;
          &lt;asp:UnLink /&gt;
  
          &lt;asp:HorizontalSeparator /&gt;
          &lt;asp:SelectAll /&gt;
          &lt;asp:UnSelect /&gt;
  
          &lt;asp:HorizontalSeparator /&gt;
          &lt;asp:RemoveFormat /&gt;
          &lt;asp:Delete /&gt;
          &lt;asp:Cut /&gt;
          &lt;asp:Copy /&gt;
          &lt;asp:Paste /&gt;
  
          &lt;asp:HorizontalSeparator /&gt;
          &lt;asp:FontNameSelector /&gt;
          &lt;asp:FontSizeSelector /&gt;
          &lt;asp:BackgroundColorSelector /&gt;
          &lt;asp:ForeColorSelector /&gt;
  
          &lt;asp:HorizontalSeparator /&gt;
          &lt;asp:InsertImage /&gt;
      &lt;/Toolbar&gt;
  &lt;asp:HtmlEditorExtender&gt;
  </code></pre>
  
  <p><strong>Codebehind</strong>:</p>
  
  <pre><code>/// &lt;summary&gt;
  /// SaveImagen HtmlEditorExtender AjaxControl
  /// &lt;/summary&gt;
  /// &lt;param name="sender"&gt;&lt;/param&gt;
  /// &lt;param name="e"&gt;&lt;/param&gt;
  protected void saveFile(object sender, AjaxControlToolkit.AjaxFileUploadEventArgs e)
  {
      if (!Directory.Exists(MapPath(_fileImgNotasPath)))
          Directory.CreateDirectory(MapPath(_fileImgNotasPath));
  
      // Generate file path
      string filePath = _fileImgNotasPath;
      filePath += HttpContext.Current.User.Identity.Name + "_";
      filePath += String.Format("{0:ddMMyyyyhhmm}", DateTime.Now);
      filePath += e.FileName.Substring(e.FileName.Length - 4, 4);
  
      // Save uploaded file to the file system
      var ajaxFileUpload = (AjaxFileUpload)sender;
      ajaxFileUpload.SaveAs(MapPath(filePath));
  
      // Update client with saved image path
      e.PostedUrl = Page.ResolveUrl(filePath);
  }
  </code></pre>
  
  <p><strong>WebConfig</strong></p>
  
  <pre><code>&lt;system.web&gt;
      ...
      &lt;sanitizer defaultProvider="HtmlAgilityPackSanitizerProvider"&gt;
          &lt;providers&gt;
              &lt;add name="HtmlAgilityPackSanitizerProvider" type="AjaxControlToolkit.Sanitizer.HtmlAgilityPackSanitizerProvider"/&gt;
          &lt;/providers&gt;
      &lt;/sanitizer&gt;
      ...
  &lt;/system.web&gt;
  </code></pre>
  
  <p><strong>References added, dll in bin folder</strong></p>
  
  <p>This worked, at some point stopped working, and update the AjaxToolKit and nothing. <strong>All other controls work</strong> :S nothing more that part of InsertImage
  What could be happening?</p>
  
  <p>help me superman!! ;)</p>