Problem with categories listing in Marketpress


I recently upgraded from Marketpress Lite to Marketpress, and now I have the following problem:

I have a side widget to show product categories. When I choose a category it does not show all products in this category, but a blog post, whose content is generated from the first book in the category.

The same thing happens if I go to Store, and then browse by category.

I use WordPress 3.5 with Montezuma theme. The site is located at: