Today when attempting to login to the administrator (administration) portion of one of my customers Joomla websites, I received an “Invalid Session” error. Internet Explorer only shows the error in the URL and just redirects you back to the login page: http://mikefrobbins.com/administrator/index.php?mosmsg=Invalid Session
You have a session directory specified in your php.ini file that does not exist:
session.save_path = “X:/my/session/directory/”
Create the directory and make sure it has the proper permissions to resolve this problem.