10.3 Clients can’t log in or authenticate to 10.3 server

I am upgrading a lab to Home Directories on 10.3 client/server, from OS 9/10.2 client/server. The clients are getting DHCP from a windows server in the 10.x.x.x range. The Mac server has a visible address at 203.10.x.x. I tested the set up using 10.2 server, during the semester. In Directory Access/Authentication , I would see root@10.x.x.x greyed out when I chose Custom Path. When I tried to add a server for directory path, all I got was BSD/Local. However, after fixing all permissions, the log-ins worked - in other words, the 'Other' option appeared and worked, delivering Group preferences. Yesterday I upgraded the server with a fresh install of 10.3 on another drive. I also installed a 10.3 client from scratch. No matter what I do in Directory access, I can't get the 'Other' log-in to appear. And on the clients which were previously set up, the 'Other' user appears briefly then vanishes. Is this because of the difference in the network addresses of the server and clients? (they are both on Class B subnets) Is there anything I can try to fix this? I would really appreciate any ideas you have. :?: