images on shopping cart are bordered

I have the wp estore plugin and when you add something to the cart the plugin puts the cart on my sidebar. anyways once something is added and you can see the sidebar, there are white borders around the images (3 of them). I cannot figure out how to get rid of them. These are png images and shouldnt be like this. I would appreciate any help with this. Here is the order page. [link moderated at user request]