Classifieds conflict with wp category ?

Hi,
I use the classifieds plugin to integrate some classifieds on my website. My website contains also some wp categories,pages, post and others custom post type.
When the plugin classified is activated ( see on the link http://troll.ws/image/5bf02ba2#.UeCC920VGSo), wordpress cannot display post under its category. I have a category Actualités ( with slug actualites containing 5 posts http://troll.ws/image/e54a62c6#.UeCDc20VGSo). I can display single post but when i click on category link or type congoexpat.fr/actualites wp does not find posts under category (http://troll.ws/image/d2f9349b#.UeCD9m0VGSo). When i desactivate the plugin my posts are shown under category. You can see on the following screen shot http://troll.ws/image/d6714e68#.UeCEU20VGSo.
Is there a setting to do with the classifieds plugin to do not alterate standard working of wordpress ?
Thanks