NT 4.0 / W2K Password Replication

We are having a Windows 2000 PDC With 2 NT 4.0 BDCS. One of the BDC’s sits at a remote location accessable over an ISDN line. When a user changes their password on the PDC there password is not replicated down to the remote BDC.

The event logis returning the following error on the remote BDC

No Windows NT Domain Controller is available for domain CWLNT. (This event
is expected and can be ignored when booting with the ‘No Net’ Hardware
Profile.) The following error occurred:
Thereare currently no logon servers available to service the logon
request.

This message comes up every 15 minutes

We can ping both the IP address and the server name, and when logging on using an old password we have full access to the network.
Any ideas??