Are you using the code I put in the message? There shouldn't be any NTP packets going across because there's nothing NTP related in that code.
It's a reliable DNS server. If I never browse to the web port on the Arduino then it'll sit there and poll forever with no issues. In fact it's been up polling for the past 3 hours and has not had a single failure. As soon as I browse to we web port though, it fails (well, I actually have to browse twice for it to happen).