all custom fields are set as default radio boxes?

[ultimamedia]

Hello all i have just uploaded 3 custom fields, all three are image type - yet when i add them to a product the radio button is checked for all 3 - how do i make one default?
http://ultimadevelopments.info/kinsey/index.php/kinsey-bags/occasion-bags/cross-body-bag-jaguar-print-detail

as you can see here all 3 are checked!
Hope someone can help!
Many thanks,
Chris