First, rule out any type of firewall/ipchains/iptables lock-out. From your client, do this:
telnet x.x.x.x 53
If you get:
Connected to dns.foo.com.
..then that rules that out. However, if you cannot connect to port 53 of x.x.x.x (your DNS server) then you're really not getting through.
If you ARE getting through, you can't resolve, you need to check your named.conf to make sure that you have it open to do name resolution for that particular client's IP address. It's often a very good idea (not sure if it ships stock) to lock down BIND so that recursive queries aren't performed for outside hosts.