I had the same problem with my DNS IP addresses on ubuntu 8.04. After each reboot were DNS records blanked. I suppose it was caused by "resolvconf" package that I had installed. This package probably overwrote DNS records in "/etc/resolv.conf" after each reboot. After uninstalling of this package is everything all right, no need to enter DNS IP addresses manualy.
I had the same problem with my DNS IP addresses on ubuntu 8.04. After each reboot were DNS records blanked. I suppose it was caused by "resolvconf" package that I had installed. This package probably overwrote DNS records in "/etc/resolv.conf" after each reboot. After uninstalling of this package is everything all right, no need to enter DNS IP addresses manualy.