You may need to clear your browser cookies to make sure you're testing the cart with a completely clean slate. I couldn't exactly reproduce what you described, but in IE8 where I have script error reporting and debugging enabled, clicking your Add to Cart buttons produced a script error because your page doesn't have any View Cart code.
Just make sure you have a complete block of View Cart code on every page with any number of Add to Carts. The View Cart code carries the programming that manages our cart display as an overlay "inside" your page, so if that code is missing, the Add to Cart buttons are trying to use a javascript function that isn't present in the page.
If you can't get the cart overlay working even after you add the View Cart code, you may need to experiment with moving around this portion of the View Cart code to various places in your page source, before or after other javascript tags you're using, until you find a position that resolves the conflict:
<script language="javascript" type="text/javascript">
<!--
function EJEJC_lc(th) { return false; }
// -->
</script>
<script src='http://www.e-junkie.com/ecom/box.js' type='text/javascript'></script>
