DHCP Client: Access is denied

I run a small network(<30 users). I have enabled DHCP on my server. On some of my clients, in Event Viewer, I receive the following error: "DHCP failed to obtain a lease for the card with Network Address (MAC address) of client. Access is denied." Searched TechNet, equates to Article ID: Q244978. However, I only have one server, the Technet articles relates to two servers running DHCP. Server is NT Server 4.0, all clients are NT Workstation 4.0. The server reports no problems with any service in Event Viewer. IPCONFIG on the clients show assigned IP address on client. Network Neighborhood shows all clients and server. Network appears to function normally. So why does the client Event Viewer report "Access is denied"?