Nameserver does not have A record

I recently upgraded BIND on my DNS server and now DNS isn't working for any of my websites. Performing an nslookup results in a timeout, and using dig on a different server tells me there are no authoritative sections returned in the query. Using dig locally on the server, however, produces the expected results.

I tried the tool found on DNSsy.com which tells me there are no A records for my nameserver, which appears to be incorrect based on my zone file. Below is one of the zone files I have configured (the actual domain names and IP addresses are substituted/masked):

example.com.zone

$ORIGIN example.com.
$TTL 1W
@       IN      SOA     ns.example.com. example.example.com.  (
                                      2011060701 ; Serial
                                      28800      ; Refresh
                                      14400      ; Retry
                                      604800     ; Expire - 1 week
                                      10800 )    ; Minimum
    IN  NS  ns
    IN  MX  10 mail

localhost IN A     127.0.0.1
@         IN A     x.x.x.x
ns        IN A     x.x.x.x
mail      IN A     x.x.x.x
www       IN CNAME @

named.conf

acl "xfer" {
        none;
};

acl "trusted" {
        127.0.0.0/8;
        ::1/128;
};

options {
        directory "/var/bind";
        pid-file "/var/run/named/named.pid";

        listen-on-v6 { ::1; };
        listen-on { 127.0.0.1; };

        allow-query {
                trusted;
        };

        allow-query-cache {
                trusted;
        };

        allow-recursion {
                trusted;
        };

        allow-transfer {
                none;
        };

        allow-update {
                none;
        };

        forward first;
        forwarders {
                8.8.8.8;                // Google Open DNS
                8.8.4.4;                // Google Open DNS
        };
};

logging {
        channel default_log {
                file "/var/log/named/named.log" versions 5 size 50M;
                print-time yes;
                print-severity yes;
                print-category yes;
        };

        category default { default_log; };
        category general { default_log; };
};

include "/etc/bind/rndc.key";
controls {
        inet 127.0.0.1 port 953 allow { 127.0.0.1/32; ::1/128; } keys { "rndc-key"; };
};

zone "." in {
        type hint;
        file "/var/bind/root.cache";
};

zone "localhost" IN {
        type master;
        file "pri/localhost.zone";
        notify no;
};

zone "127.in-addr.arpa" IN {
        type master;
        file "pri/127.zone";
        notify no;
};

zone "x.x.x.in-addr.arpa" IN {
  type master;
  file "pri/x.x.x.zone";
  notify no;
};

zone "example.com" IN {
  type master;
  file "pri/example.com.zone";
  notify no;
};

Output running named-checkconf

None, which I assume means it's okay.

Output running named-checkzone

named-checkzone example.com /var/bind/pri/example.com.zone zone example.com/IN: loaded serial 2011060701 OK