Fixing a Javascript Error on an eCommerce site

We are a luxury jewelry retailer based out of NYC looking for a second opinion on the development of our site. Namely, we're looking to fix the javascript display on this page, on which the navigation buttons (especially the left one) stop working or the images stop displaying after a minute on all browsers: http://www.paolocostagli.com/earrings/mix-match/mix-and-match.html

Our current developer put in 4 days of work and says we need to completely reconfigure the back-end to render this part of our site functional. We're looking to either confirm or disprove that statement by finding an adept and experienced Magento programmer to give us a second opinion. We don't to have two developers working on our site by any means, but we do want to explore our options.