Hmmm
Can you try removing this part:
#
<!--[if lt IE 9]>
#
<script src="https://html5shiv.googlecode.com/svn/trunk/html5.js"></script>
#
<![endif]-->
#
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js"></script>
#
#
<title><?php wp_title('',true,'right'); ?><?php bloginfo('name'); ?></title>
#
<?php if( is_singular() ) wp_enqueue_script( 'comment_reply' ); ?>
And see if that makes a difference?
Might be an error in the included code somewhere. If it does make a difference add each line back one by one to see when it happens. Is ‘html’ a legal doctype? Otherwise try this for example, see if that helps:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "https://www.w3.org/TR/html4/strict.dtd">
That is all that I can see that can be causing the problem, but I could be overlooking something.