The new bind version 9.3.6 (Redhat 5.4) try to use IPv6 transport even if the server host does not have IPv6 connectivity, resulting in slower name resolution.
To fix this you have to start the bind damon with "-4" (IPv4 only). You can add the line "OPTIONS="-4"" to /etc/sysconfig/named to do so.Sep 2 19:43:16 cpanel named[22767]: network unreachable resolving 'ns.isc.afilias-nst.info/A/IN': 2001:500:7::79#53