Multihomed DHCP server

I’ve had a strange problem on multiple W2K DC’s. The server is multihomed having a interface card on the LAN and a interface card pointing to the backbone for internet access. Internet access works fine through ISA server. The problem comes with DHCP and WINS. I can install both services, but the services can not find the server. Error message “Cannot find the server”. I’ve been looking on microsoft technet and support, but have not found a solution. DNS works fine, No firewall or filters are activated on ISA. Someone must have experienced this before.