1. Initial search results only return 2 pages, with 20 results per page. You can't see more until you advance to the next page.
2. After performing a search of a particular group (e.g. Autodesk Revit Architecture) you see results contained in that group. If you refine that search, the results apparently open up to include all the forums. Sorry, if I'm looking for a Revit solution I don't want search results from the Inventor group.