FireWall-1 and MS DNS

I just implemented Firewall-1 ver. 4.1 on a Windows NT Server. The firewall runs great however I tried to move my two DNS servers behind the firewall yesterday and had severe problems. I set up the rules just as I did for my web servers that I moved with the exception of using DNS service instead of web services. I am using automatic NAT. When I moved DNS 2 (my secondary DNS Server)DNS 1 (Primary) preformed nonstop read /write hard drive activity. When I moved DNS 1 behind the firewall theactivity did not stop and noone inside or outside the firewall could acces our internal web pages…. Internal clients could not access the internet either. What did I do wrong?? Any ideas???