On the dns seeder:
$ dig @127.0.0.1 seed.cryptodistributed.org

;<<>> DiG 9.9.5-3-Ubuntu <<>> @127.0.0.1 seed.cryptodistributed.org
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 61122
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEDUOSECTION:
; EDNS: version; 0, flags:; udp: 4096
;; QUESTION SECTION:
; seed.cryptodistributed.org.        IN        A

;; Query time: 20 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Fri Sep 19 20:23:31 EDT 2014
;; MSG SIZE rcvd: 55

On a client VPS:
$ dig @104.131.20.192 seed.cryptodistributed.org

; <<>> DiG 9.9.3-rpz2+rl.13214.22-P2-Ubuntu-1:9.9.3.dfsg.P2-4ubuntu1.1 <<>> @104.131.20.192 seed.cryptodistributed.org
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 35619
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;seed.cryptodistributed.org.   IN   A

;; Query time: 227 msec
;; SERVER: 104.131.20.192#53(104.131.20.192)
;; WHEN: Fri Sep 19 20:38:17 EDT 2014
;; MSG SIZE  rcvd: 55

Master zone file checks:

Forward zones look good:

$ named-checkzone cryptodistributed.org /etc/bind/zones/db.cryptodistributed.org
zone autun.hom /IN: loaded serial   2
Ok

$ named-checkzone cryptodistributed.org /etc/bind/zones/db.cryptodistributed.org
zone autun.hom /IN: loaded serial   2
Ok

I think I may have found the problem, it appears  that I've made a mistake in my reverse zone file:

$ names-checkzone cryptodistributed.org /etc/bind/zones/db.104.131.55
zone cryptodistributed.org/IN: NS 'ns1.cryptodistributed.org' has no address records (A or AAAA)
zone cryptodistributed.org/IN: NS 'ns2.cryptodistributed.org' has no address records (A or AAAA)
zone cryptodistributed.org/IN: not loaded due to errors

$ named-checkzone 55.131.104.in-addr.arpa /etc/bind/zones/db.104.131.55
zone 55.131.104.in-addr.arpa/IN: loaded serial 10
OK

As I understand it, I should not need to create an A record in the reverse zone file as the PTR record fulfils this function.

/etc/bind/zones/db.104.131.55

$TTL    604800
@       IN      SOA     cryptodistributed.org. admin.cryptodistributed.org. (
                              10         ; Serial
                         604800         ; Refresh
                          86400         ; Retry
                        2419200         ; Expire
                         604800 )       ; Negative Cache TTL
;

; Name servers
        IN      NS      ns1.cryptodistributed.org.
        IN      NS      ns2.cryptodistributed.org.

; PTR records
112          IN      PTR      ns1.cryptodistributed.org.
252.18      IN      PTR      ns2.cryptodistributed.org.
44.53      IN       PTR      www.cryptodistributed.org.
192.20       IN      PTR    seed.cryptodistributed.org.

Thoughts on where I've gone wrong?