DNS Cache - Requires Frequent Flushing

Greetings,

I am experiencing intermittent and sporadic issues with name resolution. I will provide an example workflow to highlight the issue:

Joe User opens 4 different websites in 4 tabs via safari or firefox on his MacBook Pro simultaneously. 3 of the 4 websites load without issue, the 1 site that does not load prompts the user with a dialog that says the computer is not connected to the internet. The website that has an issue is random and can cycle without notice - all attempts to ping the remote host by domain name fail, IP works. The issue occurs in all locations (home, work, coffee shop, etc) and is not application specific (Safari, FireFox, Network utility).

The only method that I have found resolve the websites is to open terminal and execute 'dscacheutil -flushcache' - This must be done every 15-20 mins.

I have a 2010 MacBook Pro running 10.6.7 - All updates are installed.