jquery masonry collapsing on initial page load, works fine after clicking "home" menu button

I think it's because the script is being run before the content (images) is fully loaded. Hence the positioning error.

Try this.

  $(window).load(function()
  {
      $('#content').masonry({
           itemSelector : '.product',
           columnWidth : 310,
           isAnimated: true,
           animationOptions: {
                duration: 700,
                easing: 'linear',
                queue: false
           }
      });
  });