I have been seeing many of these types of errors in server1.mydomain.com /var/log/messages:
client 192.168.1.103#33475: query 'jbstech.com.au.mydomain.com/IN' denied
client 192.168.1.103#45207: query (cache) denied
192.168.1.103 corresponds to server1's IP address on my LAN, and I never use it to run client applications.
Subnet 1 on my network is NAT'd behind a PIX firewall, but subnet 2 is not (both subnets use 192.168. series addresses). It's possible that this problem started after I implemented IP forwarding between the 2 NICs on server2 (one for each subnet), but I'm not sure. What could be causing this?