On IE (at least up to version 9), you can't properly style a [disabled] element. This short snippet aims to offer you a way around. I'm assuming you use Paul Irish's conditional classes :

// Detection of problematic elements
$('.ie8 [disabled], .ie9 [disabled]').each(function() { $(this).removeAttr('disabled').addClass('disabled'); });
$(document).on('focus', '.disabled', function() { return false; });

// Now just adapt your stylesheet by adding the extra selector .disabled to your [disabled] rules