SP2007 - EnableInheritance="True"

If you set Current Navigation to “Display the same navigation items as the parent site” and you don’t see the same navigation items as the parent site, you might need to add an EnableInheritance="True" attribute to the PublishingNavigation:PortalSiteMapDataSource as in this example:

<PublishingNavigation:PortalSiteMapDataSource ID="SiteMapDSWithHeadings" Runat="server"
    SiteMapProvider="CurrentNavSiteMapProvider"
    EnableViewState="true"
    StartFromCurrentNode="true"
    StartingNodeOffset="0"
    ShowStartingNode="false"
    TrimNonCurrentTypes="None"
    EnableInheritance="True"/>