DFS and offline file trouble.

I have moved files to a new file server where they are accessable through a domain DFS. However the choice to make the files available offline is no longer in the menus. The servers are Win2000 and the clients are winXP and they are all in an Active Directory. Files can be 'made offline' when accessed through a share but not through the DFS. How can I get the 'offline files' function to work when they are accesed through the DFS ?