Clicking on images in product display page doesnt show pic

[Pikkolo]

Hello 

Joomla version is 2.5.19, virtuemart version is 2.0.26d

Lets get this page as an example => http://www.cseitaliaclub.it/index.php?option=com_virtuemart&view=productdetails&virtuemart_product_id=39&virtuemart_category_id=19&Itemid=475

if i click on the images that are added to the product content displayed, nothing happens. Once upon a time, clicking used to show the image in a kind of lightbox, i m sorry i cant give more details but i cannot get back to the previous condition now.

Could it be that upgrading Joomla or upgrading vm or vmaio has messed up something and the lightbox now cannot work fine ?

Any way i may fix it ?

Hope somebody will help me 

Cheers