Some CNAME DNS queries fail after latest 10.6.5 update

Question

Right after rebooting from the latest MacOS X update I noticed some DNS queries are failing. These happen to be DNS queries for CNAME records. Other computers in the same network are not affected by this problem, including Mac's to wich the update was not yet installed.
Here are the simple diagnostic steps:
snowboard:~ pmsjt$ nslookup imap.texair.net.
Server: 192.168.0.14
Address: 192.168.0.14#53
imap.texair.net canonical name = taz.warner.local.
Name: taz.warner.local
Address: 192.168.0.12
snowboard:~ pmsjt$ ping imap.texair.net
ping: cannot resolve imap.texair.net: Unknown host
snowboard:~ pmsjt$
snowboard:~ pmsjt$ ping taz.warner.local
PING taz.warner.local (192.168.0.12): 56 data bytes
64 bytes from 192.168.0.12: icmp_seq=0 ttl=64 time=2.818 ms
64 bytes from 192.168.0.12: icmp_seq=1 ttl=64 time=2.211 ms
64 bytes from 192.168.0.12: icmp_seq=2 ttl=64 time=1.425 ms
64 bytes from 192.168.0.12: icmp_seq=3 ttl=64 time=2.242 ms
64 bytes from 192.168.0.12: icmp_seq=4 ttl=64 time=4.882 ms
64 bytes from 192.168.0.12: icmp_seq=5 ttl=64 time=3.190 ms
^C
--- taz.warner.local ping statistics ---
6 packets transmitted, 6 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 1.425/2.795/4.882/1.083 ms
snowboard:~ pmsjt$

Answer 1

Just as a sanity check, the second portion of the clause from the KB article doesn't apply in your situation, does it?
Additionally, Mac OS X v10.6 automatically detects when the local network operator has set up a name server that will answer name requests for a domain ending in ".local". It does this by checking to see if there is a Start Of Authority (SOA) record for the top level domain "local", which is how a DNS server indicates that it claims to have authority over a part of the DNS namespace. As long as the DNS server is properly configured with the required SOA record, Mac OS X v10.6 will detect this SOA record and automatically use this server to look up all host names in the domain.
Also, if you have time, you might want to check what mDNSResponder is actually doing by enabling logging; the man page describes the process in more detail:
LOGGING
There are several methods with which to examine mDNSResponder's internal state for debugging and
diagnostic purposes. The syslog(1) logging levels map as follows:
Error - Error messages
Warning - Client-initiated operations
Notice - Sleep proxy operations
Info - Informational messages
By default, only log level Error is logged.
A SIGUSR1 signal toggles additional logging, with Warning and Notice enabled by default:
% sudo killall -USR1 mDNSResponder
Once this logging is enabled, users can additionally use syslog(1) to change the log filter for the
process. For example, to enable log levels Emergency - Debug:
% sudo syslog -c mDNSResponder -d
A SIGUSR2 signal toggles packet logging:
% sudo killall -USR2 mDNSResponder
A SIGINFO signal will dump a snapshot summary of the internal state to /var/log/system.log:
% sudo killall -INFO mDNSResponder
http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/ man8/mDNSResponder.8.html
I suspect in this case packet logging might be most informative.