We have a few computers that run DHCP from our DC and most of the time they run fine, but every so often we will get a call that they cannot access the internet. I do an ipconfig /all and the DNS Server values have changed to an IP address that doesn't exist on our network. Also noticed that, at least on one occasion that DNS Suffix Search List removed one of ours and replaced it with mshome.net. If we reboot the machines they are back to working normally. I also didn't notice anything running on one of the machines that would tip me off to the cause.