DHCP Problem with 2003 DC

Hi all,
we have upgrade our 2000 forst to 2003, it contain 1 parent domain and 2
child domain, one of dc in a child domain will act as a DHCP server, after
installing the DHCP service , configured the scop, activated and authorized
in AD, every thing is just fine no errors in logs but DHCP server dosn't
provide an ip's to any client , i installed another 2003 server (member
server) to act as DHCP server it is working and can provide ip's to the
client after i ran dcpromo to this server it is stoped to provide any ip's
again with no error in log's,