Connecting to a Mac OS X server

Well, for a start, Go -> Connect to Server will only look for servers on the local network. You don't say if the servers are local or remote, but the problem could be as simple as that.

Try to connect manually by typing the IP to "Server Address:" field.
afp://192.168.x.x/

First, have your new workstations been provided with the address of your local DNS (Domain Name Server), either by direct configuration or by including it with DHCP information passed out by your Router?

Next, on your new workstations, you can use the "Directory Access" Application to provide LDAPv3 (Lightweight Directory Access Protocol) configuration information [at least the FQDN (Fully Qualified Domain Name) of the Open Directory Master] and add that LDAP server name to the search path. This step will be needed if you expect to log on to accounts stored on the Server.