Gene, the specific command to run is:
sudo /usr/sbin/tcpdump -s 0 -i en0 -w /tmp/tcpdump.out 'port 53'
(In that command, "en0" means you're using a wired Ethernet
connection. If you're using a wireless connection, run that same
command, but use "en1" instead of "en0".)
Start this in a Terminal window, then try to do streaming. If the
streaming fails, go back to the Terminal window, hit ctrl-C to
interrupt tcpdump, and e-mail the file /tmp/tcpdump.out to the list,
or (better) to any member of the Google Public DNS team.
Hope this helps. --PSRC (Google Public DNS software engineer)