category view with 1 product view url possible?

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Hi,
I've trying & searching today, but I can't figure this out.
For a client I made a menu with 2 category views and 1 product view.

The menu is like this:
- catalogus (category view, shows 3 categories when cklicked. )
-- submenuitem1 (product view, shows all products in a category. )
-- submenuitem2 (category view, shows all subcategories in a category.)
-- submenuitem3 (category view, shows all subcategories in a category.)

When "catalogus" is clicked, 3 category views appear, and the links of the shown categories 2 and 3work as they do in the menu.(Here is an url: www.liams.nl/js/ ) But the first category that is displayed, representing menuitem1 in product view in the menu, displays as a category view also. The strange thing is, the url has /category/ in it, and item 2 and 3 do not have this. I have tried to solve this with a hidden menu and a associated irems module, but no matter what I do it keeps showing categories in stead of products.

So I must be doing something wrong , but have no idea what it would be. Any help would be appreciated!!
Thanks,
Roy

Here is the url: (removed old url)
it shows 3 categories. The first one I would like to display products in stead of subcategories.
thanks!

I allready 'FIxed' it by creating a second horizontal menu with images. Sort of frustrating, but it works for now.
I will sure try to do a permantent fix you suggested Nicolas.