Important Notice Users updating to CentOS 3.5 from CentOS 3.4 may experience a problem with /etc/named.conf reverting to the default state. This is due to a problem with the new caching-nameserver rpm provided with CentOS 3.5. If the problem does occur, it can be easily corrected by running the following command in a root shell:
Do you have an /etc/named.conf file existing then? Or any backup/saved file of it? Perhaps in your server's backup itself then? How many domains/entries do you have (or did you have) in the named.conf file? If you have nothing and a lot of domains, you can write a script script or run a quick command in shell to automatically rebuild it from the list of domains in /var/named or /etc/namedb, so it's nothing to be too stressed out about. If there's an issue with the error due to the notice, there's a few ways to deal with and fix it, so not to worry. What is the nature of the problem you are currently facing?