Cannot set featured image

I am suddenly having problems loading a featured image on my Product Pages. I am using WP eCommerce, and the product pages work exactly the same as pages and posts. I can upload images to my media library, and also I can attach the image to my product page. But the Media Library link in the “set featured image” section does not work. I just updated to the latest WP version, which often fixes these issues. I need help, please!