Disable the IPV6 in BIND. For CentOS 5.4, edit the /etc/sysconfig/named file and add the following options into the BIND startup

OPTIONS=”-4″

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.