Symptoms
Since switching to a new skin, the site throws "Object Expected" and other JS errors when trying to add items to the cart/wishlist/etc.
Cause
Many of our pages use JavaScript validation, so we expect the skin template file to add include that script, so that it is on all pages.
Solution
To include it in your skin, add the following line in the <head> section:
<script type="text/javascript" src="jscripts/formValidate.js"></script>