I just wanted to post a little tidbit about the newer versions of DNN.  Specifically, I just installed DNN 4.8.4.  It went through the install process just fine and after that I tried to open the home page of the default portal.  I got stuck in an endless loop of redirects back to the home page.  In previous versions of DNN, this behavior was usually a result of a misconfigured PortalAlias table.  After spending time troubleshooting it from that angle I had to just start debugging the code.  I found a gem in the Page_Error handler in PageBase.vb that was causing my issue.

If objBasePortalException.Message.Contains("System.Web.Extensions") Then
    ' suppress AJAX error in Medium Trust
    Response.Redirect(strURL)

Googling for the exception message led me to this post http://www.dotnetnuke.com/Community/Forums/tabid/795/forumid/111/threadid/200731/scope/posts/Default.aspx.  Because I am using VS2008, my solution was to change the web site build settings to target the 3.5 framework instead of 2.0 so that the build would include references to ASP.NET AJAX.  Changing the build target to 3.5 fixed the problem.