Swap Image and Horizontal/Vertical Loops in PHP

Unfortunately the site I'm working on is only live on my local server so I can't link to it.

What I have is a detail page that's getting the item_id passed to it in the URL. I've got a large image, some details, and several thumb images of the item on the page. I'm getting the thumbs to display the way I want by using a horizontal looper. I want to swap out the large image for a large version of the thumb. I know it sounds simple, it's just not working. I get the large image to disappear onClick, but no swap occurs.

I've tried several different recordsets for the swap, but nothing.
I think this problem is staring me in the face, but I just can't see it.
Any Ideas?

Many Thanks,
Rick Hart

It works fine for me!

Can you give us a link to the page, and what you perceive is not working?