@Sebastian - Thanks for the scripts, I executed them and then re-built the search index.  I then verified that there is in fact the expected data in the SearchItem, SearchItemWord, SearchItemWordPosition, and SearchWord tables.  The SearchIndexer table is however empty (which I have no idea if it should be or not).

@Mark I did verify that the SearchCrawler Results Settings of the search module does include the appropriate results scope, though I think Sebastian was saying that this relates to different functionality.

Could it have anything to do with the fact that ALL of the content on my site requires a particular role for view permissions?  This is an intranet site, and so all users who connect to it via active directory have a role named PFC.  Every page on the site is view-able only to that role because all of our sister companies share the same network.  Based on the company role they have, we customize the content being delivered.

Additionally, we are running the professional version of DNN for our intranet.  We also have a test install which is the community version.  The test install search functionality is working properly using the same role permissions for the pages.

Any other thoughts?  I am truly stuck here. 

Solution found (thanks to the DotNetNuke Technical Support Team). The Professional version of DotNetNuke uses the Web Crawler Search Results module on the Search Results page by default. I didn't want to use the Web Crawler Search Engine, so I had not enabled it in the Schedule screen.

What I missed was that in order to use the standard Search Results, I had to drop that module onto the Search Results page, and remove the other since I was not using it. This only applies to Professional and Enterprise installs of DotNetNuke. The community edition does not include the Web Crawler.

Thanks to everyone for your help!