After migrating a SharePoint 2007 farm to SharePoint 2010, you may find that the "Navigate Up" button is broken.  When clicked, rather than providing the expected breadcrumb/tree view, you receive "This page location is:".  To resolve the problem, open the site's default.aspx in SharePoint Designer and look for a line that reads:

<asp:Content ContentPlaceHolderId="PlaceHolderTitleBreadcrumb" runat="server" />

Remove the line, save the file and refresh the page.  The "Navigate Up" button should work properly now.