I've been doing server upgrades this week. I move some sites from one server (MacOSX 10.7.5) to the new server (MacOSX 10.8). The ip's are the same. Databases are local. Files were moved via ditto command from one box to a backup drive, then ditto from the backup drive to the new server. Old Server was shut down. New server working fine. recovered the databases. Data looked good. Files have good permissions. Website were loading fine. Sites with .htaccess files working properly. However, sites running on 5.6.x unable to login in. Now when I say that. I mean I am not getting a login failure. The page url tries to go to the dashboard but before the page can fully load I'm dumped back to the home page and I'm not logged in. Check permissions. Check the database. Check the footer.php files. Tried to recover password - no joy. Tried changing password_salt - no joy. Tried changing password in db - no joy. Tried replacing concrete folder - no joy. Removed any cache files or temp files - no Joy. Replaced concrete folder with 5.5.2.1 - joy! Tried to upgrade from 5.5.2.1 - no joy. At wits end.