Frame Relay and NT4.0 installation

I am having fun (not), trying to configure an NT4 server running DHCP/TCP/IP and a Cisco frame relay router. At the moment the router is connected to a hub on the network, the server sees it and is able to connect to the internet but none of the workstations are able to ping the router. The ISP is only telling me everything is fine up to the router and the ethernet connection. No help from them.