All of a sudden I started to get this errors when trying to log into my domain after adding two windows 2008 R2 domain controllers to my domain.
I added two new 2k8 domain controllers and powered down the old 2k3 server. But I mistakenly did not remove the old 2k3 server from the domain, so it appears servers were trying to use this server for logins. I think it had the role of infrastructure master. So I powered it back on and logins from servers and desktops worked again. I probably need to do a dcpromo and remove the old server from the domain as a domain controller first and then I should be able to just use the 2k8 servers.