This machine has no IPV6 routes in its routing table and no IPV6 addresses configured on its interfaces. The kernel has full IPV6 facilities. Except that on startup, rc, ifconfig, route, sysctl and friends are set to not configure [or remove] any IPV6 parameters.
Calling named as follows solves the problem: /usr/local/bind951b1/sbin/named -c /dev/null -g -4 And 100% of queries work. As opposed to anywhere from 0% to 100% before. As to why this solves it, I've no idea why at the moment.
