This Site: and This List: Search Scopes not working

If your "default" url in Alternate Access Mappings and the url used in the content source are different, then you will have this issue.

If your default URL is http://servername and you have an addtional URL for the same web app in the alternate access mappings, say http://sharepoint and if you use http://sharepoint in your content source, the crawl works fine without any errors but when searching via one of the contextual scopes (This Site:, This List), you will not get any results.