We are sorry but this feature is not yet working. The problem is a general one which has affects in many places on the site. It goes like this…
Sometimes one wants to do a search and display results that delivers contents based on two attributes. Searching all blogs would be doing it on one attribute – is it a blog or not, if yes, display the link? Displaying blogs by writers, or Sustainers, or Joe, or Blogs on Vision, etc., and ditto for other types of content, or combinations, would be a search on two attributes.
Oddly, WordPress makes searching on two attributes a bit tortured and we are still working on delivering it. This is the largest remaining “problem” with the new incarnation of ZCommunications. It affects the top menu in various places – for example, blogs and commentaries, it affects left side menus in various places, and it affects the search page options, too – which will become much richer once this issue is dealt with.
We appreciate your patience!