I've just downloaded the latest release of HTML5 BoilerPlate using Initializr with Respond built in, but when I run this in IE8 I get a lovely ActiveX prompt (which is probably because I'm running locally) but more worryingly I get an 'Access Denied' error on line 285 of your source script, namely:
req.open("GET", url, true);
Is this purely because I'm running locally from a file? I don't get this in any other web browsers.
This is happening because it is running from a local file. You'll want to make sure you're running this on a local webserver (changing the hosts works nicely for this)