title: Modal popup extender not displaying popup
body: <p>I have inherited some code using an ASP modal popup extender and for some reason it has now decided to stop working. Am I missing anything here? I'm not too fluent with AJAX / ASP.Net right now so im struggling to diagnose what is going wrong here.</p>
  
  <p>So firstly the javascript method that displays the modal</p>
  
  <pre><code> function ShowModalRemoveEvent(ID, EventID, InstructorID, InstructorName)
        {
           alert("Hi");
           var modal = $find('ModalPopupExtender1');
           modal.show();
           document.getElementById("txtID").value = ID;
           document.getElementById("txtEventID").value = EventID;
           document.getElementById("txtInstructorID").value = InstructorID;
           document.getElementById("txtInstructorName").value = InstructorName;
        }
  </code></pre>
  
  <p>I know this is being called because of the alert. So I would assume the prpblem is either in finding the ModalPopupExtender1 or the modal.show() line. </p>
  
  <p>Here is the code for my modal popup extender</p>
  
  <pre><code> &lt;asp:UpdatePanel ID="UpdatePanel4" runat="server" UpdateMode="Conditional"&gt;
        &lt;ContentTemplate&gt;
           &lt;asp:Panel ID="Panel4" runat="server" Style="display: none" CssClass="ModalBackground"&gt;
              &lt;table style="width: 100%" border="0" cellpadding="0" cellspacing="0"&gt;
                 &lt;tr&gt;
                    &lt;td width="7%" class="cellAlertHeader"&gt;
                       &lt;img src="../../../images/Ops/window_delete.png" style="width: 18px; height: 18px" alt=""/&gt;
                    &lt;/td&gt;
                    &lt;td width="93%" class="cellAlertHeader"&gt;
                       &lt;b&gt;Cancel Instructor Event&lt;/b&gt;
                    &lt;/td&gt;
                 &lt;/tr&gt;
              &lt;/table&gt;
              &lt;table width="100%"&gt;
                 &lt;tr&gt;
                    &lt;td width="5%"&gt;
                       &amp;nbsp;&lt;td width="95%"&gt;
                          &amp;nbsp;
                          &lt;asp:TextBox ID="txtID" Style="display: none" runat="server" CssClass="TextboxTitle"&gt;&lt;/asp:TextBox&gt;
                          &lt;asp:TextBox ID="txtEventID" Style="display: none" runat="server" CssClass="TextboxTitle"&gt;&lt;/asp:TextBox&gt;
                       &lt;/td&gt;
                 &lt;/tr&gt;
                 &lt;tr&gt;
                    &lt;td width="5%"&gt;
                       &amp;nbsp;
                    &lt;/td&gt;
                    &lt;td width="95%"&gt;
                       &lt;asp:TextBox ID="txtInstructorID" Style="display: none" runat="server" BorderStyle="None"
                          CssClass="TextboxTitle"&gt;&lt;/asp:TextBox&gt;
                       &lt;asp:TextBox ID="txtInstructorName" Style="font-size: 12px" runat="server" BorderStyle="None"
                          CssClass="TextboxTitle" BorderWidth="0"&gt;&lt;/asp:TextBox&gt;
                    &lt;/td&gt;
                 &lt;/tr&gt;
                 &lt;tr&gt;
                    &lt;td width="5%"&gt;
                       &amp;nbsp;
                    &lt;/td&gt;
                    &lt;td width="95%"&gt;
                       &amp;nbsp;
                    &lt;/td&gt;
                 &lt;/tr&gt;
                 &lt;tr&gt;
                    &lt;td width="5%"&gt;
                       &amp;nbsp;
                    &lt;/td&gt;
                    &lt;td width="95%"&gt;
                       &lt;asp:Label ID="Label2" runat="server" Text="Are you sure you want to remove this Event?"
                          CssClass="TextboxTitle"&gt;&lt;/asp:Label&gt;
                    &lt;/td&gt;
                 &lt;/tr&gt;
                 &lt;tr&gt;
                    &lt;td width="5%"&gt;
                       &amp;nbsp;
                    &lt;/td&gt;
                    &lt;td width="95%"&gt;
                       &amp;nbsp;
                    &lt;/td&gt;
                 &lt;/tr&gt;
                 &lt;tr&gt;
                    &lt;td width="5%"&gt;
                       &amp;nbsp;
                    &lt;/td&gt;
                    &lt;td width="95%"&gt;
                       &lt;asp:Button ID="ButtonConfirmRemove" runat="server" Text="Confirm" CssClass="buttonshort" /&gt;
                       &lt;asp:Button ID="ButtonCancel" runat="server" Text="Cancel" CssClass="buttonshort" /&gt;
                    &lt;/td&gt;
                 &lt;/tr&gt;
                 &lt;tr&gt;
                    &lt;td width="5%"&gt;
                       &amp;nbsp;
                    &lt;/td&gt;
                    &lt;td width="95%"&gt;
                       &amp;nbsp;
                    &lt;/td&gt;
                 &lt;/tr&gt;
              &lt;/table&gt;
           &lt;/asp:Panel&gt;
           &lt;asp:Button runat="server" ID="dummyButton" Style="display: none" /&gt;
           &lt;cc1:ModalPopupExtender ID="ModalPopupExtender1" 
                                   runat="server" 
                                   PopupControlID="Panel4"
                                   TargetControlID="dummyButton" 
                                   BackgroundCssClass="ModalBGOpacity" 
                                   CancelControlID="ButtonCancel"
                                   OnCancelScript="HideModalPopup()"&gt;
           &lt;/cc1:ModalPopupExtender&gt;
        &lt;/ContentTemplate&gt;
        &lt;Triggers&gt;
           &lt;asp:AsyncPostBackTrigger ControlID="dummyButton" /&gt;
        &lt;/Triggers&gt;
     &lt;/asp:UpdatePanel&gt;
  </code></pre>