No Domain Controller

I have a domain controller on my network. Service installed is DHCP,DNS, WINS server. My client is mix windows 98 and windows xp professional. The problem is that in my windows 98, they cant log on to the domain controller which is windows 2000 advanced server if their ip address is server assign, but if i put static ip addres in my windows 98 client they can log on to the domain controller. I have no problem in my xp but only in windows 98 client.

Pls help...
Thanks in advanced...