Event ID – 1051 :

Event ID – 1051 :
Issue: The users will not be leased an IP Address if their lease has expired or they restart their computers.
Description: The DHCP/BINL service has determined that it is not authorized to service clients on this network for the Windows domain.
Action Needed: Please verify if the client is authorizing another DHCP Server in the network or changing the IP address of the original DHCP server or if there are two DHCP servers in the network."
"Ref Link:
http://support.microsoft.com/kb/306925/en-us