If I can cross reference, http://www.gnutellaforums.com/open-d...d-results.html. You might be going through a period of not being connected to ultrapeers who are within scope of the files you are seeking.
I've gone through periods of not getting search results. One reason suggested to me was if searching the same search term(s) too frequently, the UP's can start to block it (not respond to it.) This usually repairs after a period of time (especially if you have a dynamic ip address.)

Also try doing single search criteria searches. eg: artist or title or album for music, title or ... for video, etc.