I have a XA 6.5 Farm on W2K8R2 SP1 servers. One of my new server builds is not creating the session properly. This is a Windows issue, not a XA issue. I recreated group membership for local users. When launching any application the session runs through applying policies, gets to 'Preparing your desktop', then 'logging off'. Neither of the below apply. This occurs for users and admins.
http://technet.microsoft.com/en-us/library/cc733957%28v=ws.10%29.aspx
http://social.technet.microsoft.com/Forums/windowsserver/en-US/0340b1c2-2709-4293-8d75-a58a2a92b980/logon-hanging-on-windows-2008-dc-with-all-other-accounts-than-administrator