Originally posted here by SirDice
Have you tried sniffing the DNS traffic to see what exactly is going on?
Yeah, we could see such traffic as, trying to connect to first DNS, which failed, tried secondary, which failed, tried third successfully, and then the workstation is stuck on this stupid external ISP DNS... but couldn't figure out why they fail connecting to the first and secondary, while sometimes it does work... just the majority of the times it fails...

Thanks!