[falko]

Just found this:

mh1:~# dig ns markberrymusic.com

; <<>> DiG 9.3.4 <<>> ns markberrymusic.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29695
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;markberrymusic.com.            IN      NS

;; ANSWER SECTION:
markberrymusic.com.     86400   IN      NS      ns1.nameresolve.com.
markberrymusic.com.     86400   IN      NS      ns1.mbitservices.com.au.

;; Query time: 343 msec
;; SERVER: 213.133.98.98#53(213.133.98.98)
;; WHEN: Sat Sep 24 11:39:28 2011
;; MSG SIZE  rcvd: 103

mh1:~# dig ns openheartliving.com

; <<>> DiG 9.3.4 <<>> ns openheartliving.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6606
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;openheartliving.com.           IN      NS

;; ANSWER SECTION:
openheartliving.com.    86400   IN      NS      ns1.mbitservices.com.au.
openheartliving.com.    86400   IN      NS      ns1.nameresolve.com.

;; Query time: 345 msec
;; SERVER: 213.133.98.98#53(213.133.98.98)
;; WHEN: Sat Sep 24 11:39:40 2011
;; MSG SIZE  rcvd: 104

mh1:~#

Both not-working domains use ns1.nameresolve.com as one nameserver, while the working domain mbitservices.com.au uses ns1.mbitservices.com.au and ns2.mbitservices.com.au.