It's probably been added by hand. In the TCP/IP properties of the interface you'll find an "Advanced" button. Have a look at the DNS tab, I'm sure it's been added there.
Nope there wasn't anything there, rather I have myself added the original DNS server entries there as well. But again after enabling the DNS cache getting the same issue.
One machine can do the work of fifty ordinary men. No machine can do the work of one extraordinary man!