Like I said, look at your page source for a line like this:
HTML Code:
<!-- CSS Stylesheet -->
<style type="text/css" id="vbulletin_css">
/**
* vBulletin 3.8.0 CSS
* Style: 'Testing'; Style ID: 26
*/
@import url("xxxxxx/clientscript/vbulletin_css/style-301d8672-00026.css");
</style>
What does yours look like? (Or do you even have them as files?)
I'm really not able to help with this much since I don't have IE. You can try running your page through an html validator and see what shows up.