I remove this from function.php, then it works.
$cufon_header_script = "\n<script src=\"".get_bloginfo('template_directory')."/js/cufon-yui.js\" type=\"text/javascript\"></script>\n<script src=\"".get_bloginfo('template_directory')."/js/vera.font.js\" type=\"text/javascript\"></script><script type=\"text/javascript\">/*<![CDATA[*/Cufon.replace(['h1','h2'], { fontFamily: 'Vera' });/*]]>*/</script>";
if($cufon_extra == 1) $cufon_header_script = str_replace("vera.font.js", "vera_extra.font.js", $cufon_header_script);
[Please post code snippets between backticks or use the code button.]
The problem is it use HTML5 canvas to draw the title, using Vera fonts, however this font only support English characters. My site is Chinese, so all the title are broken.
This problem not only happens in IE9. Any HTML 5 supported browsers have the problem, such as Chrome, Firefox.