I want to share my experience when i had to divide my network into Vlan. I used Win 2003 as DHCP Server and Cisco device to manage Vlan. firstly i created IP address scope for each Vlan, then i created Vlan in Ciso device. so what’s happened ? Clients at each Vlan couldn’t get IP addresses via DHCP server. Many ways i tried to solve this trouble but still had no result. Fortunately i tried to erase all my configuration in my DHCP server and my cisco switch, then i created the Vlan first then i created DHCP scope in Win 2003. Finally all clients could get ip address. I can’t explain this case technically, but i think Vlan must be defined first  then followed by IP address we will give into Vlan. Mmmhhh…maybe my explanation doesn’t satisfy you. When we meet the trouble, sometimes we don’t need many explanations..what we need just to solve the trouble. And trust me what i wrote above was really work ! ;D