You have to review your daemon logs very carefuly, I have a post entry on how to do that.
What you should at least make sure for instance is the DHCPREQUEST and DHCPACK via you logs, maybe you have a host based definition, if you could include your settings will be useful, I wrote how to create a fast DHCP maybe you just need a fresh start. DHCP Howto
For example an output delivering DHCP information should look like:
Feb 15 10:03:22 debian dhcpd: DHCPREQUEST for 172.16.32.12 from 00:21:70:9b:da:fa via eth3
Feb 15 10:03:22 debian dhcpd: DHCPACK on 172.16.32.12 to 00:21:70:9b:da:fa via eth3
Just match the MAC address and make sure you're the one giving the IP address.