I stumbled upon an HTML5 Internet Explorer shiv issue today. It seems that the WordPress TwentyEleven theme was not including the html5 shiv script properly at some point in the past. I discovered this when a forked TwentyEleven theme started throwing weird “shiv”-related text at the top of my pages.
To solve the problem, I simply copy-and-pasted the following script into my header, while removing the old code:
<!--[if lt IE 9]> <script src="//html5shiv.googlecode.com/svn/trunk/html5.js"></script> <![endif]-->