Ajax HtmlEditorExtender not rendering content

Trying to load an html file into the AJAX HtmlEditorExtender textbox in the onload event. I also tried the Pre-Load event.

I haven't worked with AJAX in awhile so I am pretty sure I am missing something simple.

        Dim myHtml As String
        Dim fileName As String = "myHTMLFile.htm"
        Dim fullFileName As String = Request.MapPath(Convert.ToString("~/Template/") & fileName)
        Dim streamReader As New StreamReader(New FileStream(fullFileName, FileMode.Open, FileAccess.Read))
        newHtml = streamReader.ReadToEnd()
        streamReader.Close()

        TextBox1.Text = newHtml

Break point shows the file content, its just not rendering.
Could someone clue me in on what I am sure is simple mistake or oversight?

thanks,