How do I flush the DNS cache on Mac OS X?
The DNS cache stores the server IP addresses locally that were accessed recently from your computer. The IP address of our servers change at regular intervals, which may lead to cache misses and connection problems if the change occurs before the entry in your DNS cache updates.
To perform this action, you must run the command from the Mac OS terminal, found in the Utilities folder. To flush the DNS in Mac OS 10.5.x or newer, type: