I don't see any problems...using your example
[carl@mars ~]$ dig www.tunnelbroker.net. @74.82.42.42
; <<>> DiG 9.6.2-P2 <<>> www.tunnelbroker.net. @74.82.42.42
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29382
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.tunnelbroker.net. IN A
;; ANSWER SECTION:
www.tunnelbroker.net. 21841 IN CNAME tunnelbroker.net.
tunnelbroker.net. 21841 IN A 64.62.200.2
;; Query time: 290 msec
;; SERVER: 74.82.42.42#53(74.82.42.42)
;; WHEN: Tue Dec 7 09:56:31 2010
;; MSG SIZE rcvd: 68
[carl@mars ~]$ dig www.tunnelbroker.net. @2001:470:20::2
; <<>> DiG 9.6.2-P2 <<>> www.tunnelbroker.net. @2001:470:20::2
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47579
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.tunnelbroker.net. IN A
;; ANSWER SECTION:
www.tunnelbroker.net. 86400 IN CNAME tunnelbroker.net.
tunnelbroker.net. 86400 IN A 64.62.200.2
;; Query time: 291 msec
;; SERVER: 2001:470:20::2#53(2001:470:20::2)
;; WHEN: Tue Dec 7 09:56:48 2010
;; MSG SIZE rcvd: 68