DNS name resolution

We just installed a new server with Windows 2000 server and removed our old Small Business Server NT 4.0 server. We have mostly Win 98 clients, but we also have 2 Win 2000 Professional clients. We have a DNS and a DHCP server set up. All the clients are getting addresses and can use network file and print resources. The Win 98 clients can surf the internet just fine. However, the 2 Win 2000 clients cannot. I can enter external addresses explicitly and it will work just fine on these machines, but they will not resolve domain names. That is the only thing they won’t do. How come my Win 98 clients are resolving just fine, and my Win 2000 clients will not? I know it is a DNS issue, but I can’t seem to track it down.