nslookup & dig fail; ping, traceroute, and scutil -r work I'm running on 10.8.2.  All of a sudden, traditional nameserver lookups are failing on my machine:

$ nslookup www.att.com
;; connection timed out; no servers could be reached

$ dig www.att.com

; &lt;&lt;&gt;&gt; DiG 9.8.3-P1 &lt;&lt;&gt;&gt; www.att.com
;; global options: +cmd
;; connection timed out; no servers could be reached


But operations that use name services work fine:

$ scutil -r www.att.com
Reachable


$ ping www.att.com
PING e2318.dscb.akamaiedge.net (23.1.57.145): 56 data bytes
64 bytes from 23.1.57.145: icmp_seq=0 ttl=55 time=22.862 ms
64 bytes from 23.1.57.145: icmp_seq=1 ttl=55 time=26.947 ms
^C
--- e2318.dscb.akamaiedge.net ping statistics ---
2 packets transmitted, 2 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 22.862/24.904/26.947/2.043 ms


I've tried setting the name server addresses to different destinations via the network system preference (e.g., 4.2.2.2, 208.67.222.222, 208.67.220.220, etc.) but that doesn't seem to make any difference.

I'm guessing there is an internal configuration file for the on-board DNS server that isn't getting updated, but I haven't a clue where to look for that.
I'm still not sure what was causing the problem, but after suffering from another seemingly unrelated issue, I did a complete re-install of 10.8.  I had originally upgraded from 10.6 -- though the utilities had seemed to work fine for a while after the initial upgrade, my suspicion is that I did something to some unknown-to-me configuration while attempting to diagnose/resolve the other issue (something that apparently disabled some aspects of DNS access).

After the re-install, all DNS-related utilities are now working fine.