Designating a product thumbnail breaks category grid view

Love this plug in but came across one issue on a friend’s site:
Product has 3 images
When one of them is set as the thumbnail, the grid view for the category starts using the default product view.
http://32fouettes.com/products-page/black_skirts/
Removing the thumbnail doesn’t fix it.

http://wordpress.org/extend/plugins/wp-e-commerce-grid-view/