Nameserver not resolving working domain

[Gilles Massen]

Hello,

I have a weird issue with a bind9 resolver: it fails to resolve a domainname 
that appears to be absolutely correctly configured (and which works correctly 
from another bind9 server). I even expect it to work after restarting Bind, 
but I don't want to do it yet in sake of finding what is wrong.

The host I cannot resolve is www.intervocative.com, returning no answer.
The domain is delegated to ns19 + ns20.worldnic.com.  Both are reachable. From 
the nameserver:

ns:/usr/local/named-ns/var/log # dig @localhost www.intervocative.com

; <<>> DiG 9.3.2-P1 <<>> @localhost www.intervocative.com
; (2 servers found)
;; global options:  printcmd
;; connection timed out; no servers could be reached
ns:/usr/local/named-ns/var/log # dig @ns19.worldnic.com www.intervocative.com

; <<>> DiG 9.3.2-P1 <<>> @ns19.worldnic.com www.intervocative.com
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23910
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 0

;; QUESTION SECTION:
;www.intervocative.com.         IN      A

;; ANSWER SECTION:
www.intervocative.com.  7200    IN      A       69.33.203.218

;; AUTHORITY SECTION:
intervocative.com.      7200    IN      NS      NS20.WORLDNIC.com.
intervocative.com.      7200    IN      NS      NS19.WORLDNIC.com.

;; Query time: 111 msec
;; SERVER: 205.178.190.10#53(205.178.190.10)
;; WHEN: Wed Nov 15 11:18:38 2006
;; MSG SIZE  rcvd: 102

Where could this go wrong? Our firewall isn't logging anything. Everyone is 
reachable, even through IPv6 (the only IPv6 addresses involved being those 
for a + b.gtld-servers.net).

Any hint to what to try, before I have to restart bind, would be much 
appreciated...

Best regards,
Gilles Massen