No Windows NT or Windows 2000 Domain Controller is available for domain Domain. The following error occurred:
There are currently no logon servers available to service the logon request.
Received this when logging into the domain through a VPN connection that had to traverse through various PIX firewalls and other Cisco switches. Was causing logins with roaming profiles to take over 10 minutes when they should have been ignored due to slow link detection. After calling Microsoft they recommended article Q244474 http://support.microsoft.com/?id=244474 to change Kerberos from using UDP to TCP.
After making these changes logon times were reduced from 10 minutes to under 10 seconds.