If you choose a top level category in advanced search you will have no ads displayed.
In this case: Main Omegatron Classifieds - All Ads
You need to choose a subcategory, like Main, For sale Omegatron Classifieds - All Ads
Then you will have a result.
Either we should not display top level categories in the search box or it should result in showing the ads from all subcategories, don't you think?