Originally Posted by Why

if you are having problems getting DNS to resolve, you might have the old answer cached... try flushing cache.

To flush DNS cache in Microsoft Windows (Win XP, Win ME, Win 2000):-
- Start -> Run -> type cmd
- in command prompt, type ipconfig /flushdns
- Done! You Window DNS cache has just been flush.

To flush the DNS cache in Mac OS X:-
- type dscacheutil -flushcache in your terminal to flush the DNS resolver cache.
ex: bash-2.05a$ dscacheutil -flushcache


although on a mac i usually have to run it a few times to really clear the cache.