Question : Newly configured DHCP (with reserviations) server for 2 subnets, 1 subnet not working with DHCP

I reciently configured DHCP and i"m working on transfering over from static to reserverd DHCP IPs. One subnet is working fine with DHCP, when I configure a computer 's mac address to a reserved IP address and configure the computer from static to DHCP the computer grabs the reserved IP for its mac address, but on the other subnet its not working, can someone tell me what is causing the problem?

Server 2003, XP Pro, 1 Cisco 3700 series router and a number of Cisco 3730 and 3550 switches.

Thank you,

Answer : Newly configured DHCP (with reserviations) server for 2 subnets, 1 subnet not working with DHCP

Sorry, I meant

On the router or layer3 switch, under the vlan interface or ip interface for the new subnet

eg. vlan interface

int vlan x
 ip helper-address x.x.x.x

x.x.x.x = ip address of DHCP server