resolv.conf is reset/overwritten

While troubleshooting a persistent networking issue I found that my resolv.conf was reset/overwritten shortly after changing "Locations". I need to stop this behaviour.

Correct resolv.conf looks like:
domain vf.shawcable.net
nameserver 64.59.144.18
nameserver 64.59.144.19

Changed resolv.conf looks like:
nameserver 85.255.116.125
nameserver 85.255.112.97

While this behaviour has no effect on a public internet, it causes havoc for me on my office intranet.

I have seen this as root and as a new "test" user.

My wife's iBook is at the same OS level and her resolv.conf is like my correct version, and stays that way.

Where would that second setting come from? Or how to I stop this "resetting" or "overwriting" behaviour.