If you are using the Thumbnail Viewer setting in the Detail Popup method, you may be seeing this javascript error in IE7 :
document.all.cartselect.style is null or not an object
I believe there is a missing step in the install directions for 4.1.x. If you make this change, the style gets created properly and the IE7 javascript error goes away:
In /skin1/customer/main/product.tpl, add the id cartselect to the form:
Code:
<form id="cartselect" name="orderform" method="post" action="cart.php?mode=add" onsubmit="javascript: return FormValidation();">
This was probably inadvertently left out of the install directions. It was a change made to solve an issue and is described in this
post. You may not need to make all the changes described in this post - the changes to /popups/thumbnailviewer/thumbnailviewer.js are already in the 4.1.x distribution of the mod - but the style id for cartselect was left out (at least in the download I have)