DNS Zapped by TCP/IP Packet filtering

I have a very vexing DNS/Packet filtering problem.

I have a Windows 2000 DNS server with AD integrated zones. And when I use TCP/IP filtering on the network adapter and permit port 53 UDP and 53 TCP, my workstations arent able to get DNS. (They are unable to resolve names, they can ping by IP adress)
Though if I allow all UDP, suddenly everyone has DNS. Which ports am I missing here?

If anybody has a suggestion, it would save a great deal of further hair from being uprooted from my head in frustration:)

Thanks!