resolv.conf rebuilt on reboot

Status: unresolved

The file resolv.conf, as originally appearing on the system, is somewhat broken. Contents:

search domain.invalid nameserver 192.168.254.254 nameserver 192.168.254.254

I have a little script that fixes this by writing a new resolv.conf file that specifies the nameservers used by my ISP and which eliminates the "search" line. However, upon every restart of the system, the original file reappears. I'm guessing it's something to do with the fact that I have DHCP set up -- all my machines go through an ISP-supplied gateway/router/modem, and they all run DHCP, and I think Ubuntu detected this during installation. There are some scripts in /etc/dhcp3/ that seem to have something to do with the creation of resolv.conf, but I haven't grokked them fully yet.

Questions:

1. How do I prevent my new resolv.conf file from being overwritten on reboot?
2. What's the deal with "domain.invalid"? This seems like an issue from some other config file that I need to address.
3. How would I go about fixing things so that the DHCP config scripts do their thing, but create a proper resolv.conf file?

P.S. Why is the above list not numbered? I used an <ol> tag. Must be something in the template.