No subject

Name Server:NS.UNIT5.ORG
Name Server:NS2.UNIT5.ORG
   Domain servers in listed order:
   NS.UNIT5.ORG                 207.63.250.13
   NS2.UNIT5.ORG                207.63.250.12

One NS is NOT responsive = ns2.unit5.org
Shouldn't the other NS be able to support any/all queries for this domain?
If so, I'm not having any luck with queries reaching ns.unit5.org with BIND 9.4.2:
$ host -a unit5.org
Trying "unit5.org"
Host unit5.org not found: 2(SERVFAIL)
Received 27 bytes from BIND942SERVER#53 in 1 ms

$ host -a unit5.org NS.UNIT5.ORG
Trying "unit5.org"
host: Couldn't find server 'NS.UNIT5.ORG': Temporary failure in name resolution

However, when I use the IP address of ns.unit5.org, I can get a response:
$ host -a unit5.org 207.63.250.13
Trying "unit5.org"
Using domain server:
Name: 207.63.250.13
Address: 207.63.250.13#53
Aliases:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48610
;; flags: qr aa rd; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 3
;; QUESTION SECTION:
;unit5.org.                     IN      ANY
;; ANSWER SECTION:
unit5.org.              43200   IN      SOA     ns.unit5.org. spam.unit5.org. 20070335 3600 900 1209600 43200
unit5.org.              43200   IN      MX      10 spammail.unit5.org.
unit5.org.              43200   IN      MX      200 mail.unit5.org.
unit5.org.              43200   IN      NS      ns.unit5.org.
;; ADDITIONAL SECTION:
spammail.unit5.org.     43200   IN      A       207.63.250.10
mail.unit5.org.         43200   IN      A       207.63.250.6
ns.unit5.org.           43200   IN      A       207.63.250.13
Received 179 bytes from 207.63.250.13#53 in 40 ms

Other DNS servers on the Internet are dealing with unit5.org's current configuration.
Thoughts?