We checked the
ISC BIND site and upgraded to the newest release which resolved this issue for us.
I compiled this manually, but installing from ports should be fine.
I think that you should probably get a test box with FreeBSD 7.0-STABLE installed and install the most up-to-date version of BIND on there. Migrate a couple zonefiles over there and verify it's functioning properly. Recently I went through a round of upgrades to bring all our FreeBSD servers up to a minimum of 6.3 and I am sympathetic to anyone facing something similar. I used that opportunity to define an upgrade plan for those systems which historically had been left to their own devices.
I was upgrading from 9.3, so I didn't see any unusual errors and there wasn't any service disruption. However, upgrading from 8 you might need to change the location of named in your rc.conf. I think that those earlier versions installed named in /usr/sbin and not /usr/local/sbin.