AjaxControlToolkit.HTMLEditor 处理嵌套标签JS错误

[ASPX]
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit.HTMLEditor" TagPrefix="cc1" %>

<a href="http://www.163.com">163</a>

<div>
<asp:ScriptManager ID="ScriptManager1" runat="server" />
<cc1:Editor ID="Editor1" runat="server" Width="500px" Height="300px"/>
</div>

[C#]
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Editor1.Content = HttpUtility.HtmlDecode("<p><span><h1>Test AjaxControlToolkit.HTMLEditor</h1></span></p>");

}
}

[在IE8的操作]
页面加载后，点163就报JS错误 "Microsoft JScript runtime error: Unable to get value of the property 'nodeType': object is null or undefined"