Are you sure it is just Forums or is YPN just making changes that are effecting all sites. My targeting changes on both my sites and neither are forums. Yesterday both sites were just getting RON ads then an hour later it was targeting again. I also think when they see changes to pages (like forums) they need to recrawl and that seems to take a day or two. The good news is my revenue is slowly increasing each day so they must be making improvments.