may be due to multiples in code:
<!--[if IE 7]>
<html class="ie ie7" lang="en-US">
<![endif]-->
<!--[if IE 8]>
<html class="ie ie8" lang="en-US">
<![endif]-->
If we're querying the DOM to get the language attribute of "the" <html> element, then there should only be one <html> element as seen by IE, though maybe this is somehow having an effect.
using latest 64bit build on windows 8.1 go to http://www.paciellogroup.com/resources/wat/ select doc info - show lang attributes [html:en-US] [html:en-US] is displayed
may be due to multiples in code: <!--[if IE 7]> <html class="ie ie7" lang="en-US"> <![endif]--> <!--[if IE 8]> <html class="ie ie8" lang="en-US"> <![endif]-->