DNS nuisance on MBP OS X 10.6.4 (Snow Leopard)

Question

I have seen many posts regarding a potential bug with DNS on SL (OS X 10.6.x). Some users have a recurring problem but at least get to a working state after a reboot or flushing their DNS cache.
I have upgraded to SL 10.6.4. DNS worked for a time and then inexplicably stopped working at all. No reboot or flush seems to restore normal operation. I have even removed the OPen DNS name servers from my MBP DNS configuration and also my router, reverting to those name servers assigned by my ISP (ComCast).
I can take any FQDN such as www.comcast.com or www.google.com and get a valid result using nslookup or dig. I can open a web browser and visit the site if I pass the numeric IP address returned by any of the above. But I get a server not found error if I attempt to pass the corresponding URL. Same result for ping - unknown host.
Nothing I've tried - flushing cache via dscacheutil, killing processes associated with mDnsResponder and restarting etc appears to restore normal DNS operations even for a time.
Clearly this does not affect all SL users or people would be flipping cars in the streets. Something in my config is pooched.
Any NEW ideas would be appreciated.

Answer 1

This MBP shipped with 10.5.x and I have recently installed an upgrade to 10.6. THe upgrade media installed 10.6.2 and I updated over the web to 10.6.4.
I am plugged into a LAN here, so the active device is en0:
MacBook-Pro:~ user$ ipconfig getpacket en0
op = BOOTREPLY
htype = 1
flags = 0
hlen = 6
hops = 0
xid = 1928974043
secs = 0
ciaddr = 0.0.0.0
yiaddr = 10.36.2.153
siaddr = 0.0.0.0
giaddr = 0.0.0.0
chaddr = 0:22:41:2b:74:74
sname = ?
file = ?
options:
Options count is 14
dhcpmessagetype (uint8): ACK 0x5
server_identifier (ip): 10.36.2.1
subnet_mask (ip): 255.255.255.0
lease_time (uint32): 0x3f480
option_overload (uint8): 0x3
router (ip_mult): {10.36.2.1}
domainnameserver (ip_mult): {10.36.2.210, 10.36.1.10}
domain_name (string): abledistributors.local
tftpservername (ip_mult): {49.48.46.51, 54.46.49.46}
networktime_protocolservers (ip_mult): {10.36.2.24}
option_160 (opaque):
0000 66 74 70 3a 2f 2f 50 6c 63 6d 53 70 49 70 3a 50 ftp://PlcmSpIp:P
0010 6c 63 6d 53 70 49 70 40 31 30 2e 33 36 2e 31 2e [email protected]
0020 32 32 00 22.
end (none):
end (none):
end (none):
MacBook-Pro:~ user$ ifconfig en0
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 00:22:41:2b:74:74
inet6 fe80::222:41ff:fe2b:7474%en0 prefixlen 64 scopeid 0x4
inet 10.36.2.153 netmask 0xffffff00 broadcast 10.36.2.255
media: autoselect (100baseTX <full-duplex>)
status: active