maybe i can throw in the reference to the "dnstracer" tool aswell. That's usually pretty handy to check where your bad dns data does come from. (in case you don't see the results you expected to have)..
Another tool I find incredibly useful is DNS Bajaj: http://www.zonecut.net/dns/index.cgi Good for checking the health of your DNS.
-- Marek IsalskiPartner, http://www.faelix.net/