Need help / opinion on problem with images

I'm in need of a little help. About 2 weeks ago for no apparent reason, many of the product images on our site began to no longer appear. I've reached out to some friends who helped us build and install the site, but I'm not getting a very quick reply on the matter.

I have no idea what could have happened to cause this, and I'd consider myself at a novice to intermediate level with basic html. I've viewed the source code and have noticed a difference with the images that work vs. the ones that do not.

For example, on this category page:

http://www.elisalou.com/index.php?main_page=index&cPath=18

I cannot see the image of the "Bailey Bag" but I can see it for the "Boxy Tote Bag". The image url for the Bailey Bag looks like this:

"images/IMG_2472ZEN.jpg"

But for the Boxy Tote it looks like this:

"bmz_cache/4/4791c489e4023caf7f3e236fdc6ab037.image.150x150.jpg"
Can anyone help give me a clue where to go next based on this info?

Thanks!!!

Andy