Disable the IPV6 in BIND. For CentOS 5.4, edit the /etc/sysconfig/named file and add the following options into the BIND startup
This will cause the BIND server to only resolve or use IPV4 and disable IPV6 support. Save the file and restart BIND server.
via CentOS 5 – BIND/named network unreachable resolving issue | hafizonline.net blog.
This has been going on for months and I finally noticed these errors from named filling up syslog. The above fix worked and now syslog is quiet again — the way it should be.