Your issue is a unnecessary z-index: 8888;
.product .image {
position: relative;
overflow: hidden;
z-index: 8888;
margin: 0 0 5px;
}
Lower it or add this to your CSS (below the above CSS):
.fb_iframe_widget_lift {
z-index: 8889 !important;
}
(downvotes might be caused by you not posting any code)