Reverse DNS not resolving for IPv6 addresses in BIND

Reverse DNS entries for IPv6 addresses are not working. Everything I've read on the subject says the following configuration should work:

In named.conf:

zone "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.3.0.0.0.0.0.c.7.5.0.6.2.ip6.arpa" IN {
      type master;
      file "/var/lib/bind/ipv6reverse.hosts";
      allow-update { none; };
};

In /var/lib/bind/ipv6reverse.hosts:

$TTL 2d
$ORIGIN 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.3.0.0.0.0.0.c.7.5.0.6.2.IP6.ARPA.
@       IN      SOA     ns1.domain.ca.  hostmaster.domain.ca. (
            2011051104 ; serial
            1h      ; refresh
            1h      ; retry
            20d     ; expire
            2d      ; minimum
                            )
    IN      NS      ns1.domain.ca.
    IN      NS      ns2.domain.ca.

3.2.0.0.                IN      PTR     smtp.domain.ca.

When I try to do the reverse hostname lookup, I get the following error:

# host -6 2605:7c00:3::23 2605:7c00:3::11
Using domain server:
Name: 206.12.82.130
Address: ::ffff:206.12.82.130#53
Aliases: 

Host 3.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.3.0.0.0.0.0.c.7.5.0.6.2.ip6.arpa not found: 3(NXDOMAIN)

As far as I can tell, this should be found.

The syslog for bind has some rather cryptic entries that may be related:

May 12 10:28:57 www3 named[16018]:   validating @0xb253cf10: . SOA: no valid signature found
May 12 10:28:57 www3 named[16018]:   validating @0xb253cf10: . NSEC: no valid signature found
May 12 10:28:57 www3 named[16018]:   validating @0xb253cf10: org NSEC: no valid signature found