DHCP not working on SBS 2003

I have had DHCP working on my SBS server without any issues for about 2 months since the last net work changes. I came back after the christmas break and DHCP is no longer working. There are no errors in the DHCP logs except for repeated DNS Update Failed messages for the same IP address. I tried everything I could think of and resorted to removing and recreating the DHCP scope. Unfortunatley still no change. I am really confused, particularly to the lack of error massages.