Page not found when clicking on sidebar

Hello all.

First off, a big thank you to the Atahualpa developers!

I started encountering a weird problem yesterday, and I would really appreciate your input in solving it.

My site is www.selecto.ro. As you can see, it has 2 sidebars, we'll focus on the left one. Clicking on the second item there (Rezultate Loto Powerball) will lead us to a "Not Found" page. However, I assure you that page exists. As do many others that return a "Page Not Found" message when clicking.

These items that are "not found" are all categories, I just noticed that. The pages and posts in that menu work just fine (try for instance clicking on the 1st and 3rd item in the menu, 1st is a page and 3rd is a post).

If it helps, this post: http://www.selecto.ro/139-milioane-d...28-iulie-2012/ should belong to the 2nd item in the menu... It is a mistery to me.

Any ideas?