Question : DHCP error

I get this error in the system event log on every node in my domain.  "The IP address lease 0.0.0.0 for the Network Card with network address 00A0C972BCC1 has been denied by the DHCP server xxx.xxx.xxx.xxx (The DHCP Server sent a DHCPNACK message)."  Please help! Sometimes the IP address listed is a valid IP in my subnet, other times its just 0's.
 

Answer : DHCP error

Reset the hubs/switches servicing the nodes in question as well.