URL sanitizer: disabled uppercase letters in URL hex character codes (it was causing conflicts with the Windows/Apache 2.2 alt namespace separator). Thanks Techokami for finding and reporting this bug.
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>blank_page</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<script type="text/javascript">
parent.TemplateDialog.loadCSSFiles(document);
</script>
</head>
<body id="mceTemplatePreview" class="mceContentBody">
</body>
</html>