David-
Here is what I have on my Pix and it works just great. I am using Pix 520 v6.34.
access-list 100 permit tcp any host xxx.xxx.xxx.xxx eq 53
access-list 100 permit udp any host xxx.xxx.xxx.xxx eq 53
static (inside,outside) xxx.xxx.xxx.xxx (dns_ip_address) 255.255.255.255
fixup protocol dns maximum-length 512
That should allow you to have your DNS server available to the outside for queries and transfers.
Frank