Catalog not working, what am I doing wrong?

I went in this morning and decided to add new products to my catalog. I am able to connect to the admin panel and add the products. However, 95% of the time, the ImageHandler add-on doesn't load. The page stays blank and it says done at the bottom.

Also, if I go to my webpage as a customer, it doesnt work either.
I get a HTTP 500 Internal Server Error.
I doubt this is a hosting problem as my main page, with a link to my online catalog, is loading properly.

What am I doing wrong?

Main site: http://www.couchespitchounette.com/
Online Catalog: http://couchespitchounette.com/catalog/

Anyone can help me?

-Julie

I deleted the 5 products I have added, and the catalog is now working again.

I'm not sure what went wrong.

I'll try to add them again later on, and I'll see how it goes.