title: I get a "Microsoft JScript runtime error: Object doesn't support this property or method" error for anything with autopostback=true on one of my pages
body: <p>I have a .NET application with the following aspx code:</p>
  
  <pre><code>&lt;%@ Page Language="C#" AutoEventWireup="True" CodeBehind="Default.aspx.cs" Inherits="WebApplication1.Default"%&gt;
  &lt;%@ Register TagPrefix="asp" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit"%&gt;
  &lt;%@ Register assembly="Telerik.Web.UI" namespace="Telerik.Web.UI" tagprefix="telerik"%&gt;
  
  &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
  
  &lt;html xmlns="http://www.w3.org/1999/xhtml" &gt;
  
  &lt;body&gt;
  &lt;form id="form1" runat="server"&gt;
  
  &lt;asp:ToolkitScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="true"&gt;
  &lt;/asp:ToolkitScriptManager&gt;
  &lt;table&gt;
  &lt;tr&gt;
  &lt;td&gt;
      &lt;asp:RadioButtonList ID="rblTest" runat="server" AutoPostBack="True" 
          onselectedindexchanged="rblTest_SelectedIndexChanged"&gt;
          &lt;asp:ListItem Text="1" Value="1"&gt;&lt;/asp:ListItem&gt;
          &lt;asp:ListItem Text="2" Value="2"&gt;&lt;/asp:ListItem&gt;
      &lt;/asp:RadioButtonList&gt;
  &lt;/td&gt;
  &lt;td&gt;
      &lt;asp:PlaceHolder ID="ph1" runat="server" Visible="False"&gt;
          Some text
      &lt;/asp:PlaceHolder&gt;
  &lt;/td&gt;
  &lt;/tr&gt;
  &lt;/table&gt;
  &lt;/form&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>I then have a C# method as follows:</p>
  
  <pre><code>protected void rblTest_SelectedIndexChanged(object sender, EventArgs e)
  {
      if (rblTest.SelectedValue == "2")
          ph1.Visible = true;
      else
          ph1.Visible = false;
  }
  </code></pre>
  
  <p>Below is where the crash occurred. It crashes any time I use a control that has autopostback=true. I use the same syntax on about 15 other forms and those all work just fine. Am I missing a property somewhere or is there something wrong with my method? I originally had an UpdatePanel around the controls and I plan on adding it again, but I need to get the postback working first.</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
  //&lt;![CDATA[
  var theForm = document.forms['Default'];
  if (!theForm) {
      theForm = document.Default;
  }
  function __doPostBack(eventTarget, eventArgument) {
      if (!theForm.onsubmit || (theForm.onsubmit() != false)) {
          theForm.__EVENTTARGET.value = eventTarget;
          theForm.__EVENTARGUMENT.value = eventArgument;
          theForm.submit();             &lt;-----Crashed at this line.
      }
  }
  //]]&gt;
  &lt;/script&gt;
  </code></pre>
  
  <p>What am I missing or is there some common mistake that I may have made somewhere? Thanks in advance for your help.</p>