A hotfix is available to support the DFS Namespaces Client failback feature on Windows Server 2003 SP1-based computers and on Windows XP SP2-based computers
In Microsoft Windows Server 2003, the Distributed File System technology is renamed to DFS Namespaces. In Windows Server 2003 SP1 and Windows Server 2003 R2, some new DFS Namespaces features are available. One of these features is named Client failback. You can use the new user interface that is available in Windows Server 2003 SP1 and in Windows Server 2003 R2 together with the hotfix that is described in this Microsoft Knowledge Base article to configure client computers to fail back to a preferred, local server if the connection to that local server is restored.

http://support.microsoft.com/kb/898900