We had to remove one of our domain controllers from our AD environment. This DC was also the Certificate Authority for the domain. We installed the CA role on a new (non DC) member server with the same CA name but a different server name. There were various issues with issuing certificates from the new but we appear to have them all fixed now.
After running dcpromo to demote this domain controller, within a week all of our macs that run mountain lion stopped connecting to AD. We had to put local logons onto the macs. Now trying to bind the Mountain Lion macs to our Windows 2008 R2 network, I get "Unable to connect to server". I can update DHCP on the mac with no problems, so it talks to the network OK, and gets the proper DNS servers.
Our Snow Leopard macs do not have this problem, they remained connected to the network.
For a while we were having issues with secure ldap connections to our domain controllers using port 636, but we contacted Microsoft and resolve this issue. (not sure if that is relevant, but want to give all information). We have checked out many articles but none of them have helped the issue.
I don't see any connection attempts on either of our 2 domain controllers coming from the macs. I can't get a good error message - one of the only seemingly relevant messages coming from the mac is:
"opendirectoryd: GSSAPI Error: A token was invali (unknown mech-code 0 for mech unknown)"