Nginx – Can’t restart nginx, bind() failed (98: Address already in use)

I know this topic exists in various different forms, but I'm having trouble solving my problem. If I run service nginx restart, nginx fails with the following log:

2015/03/14 08:36:42 [emerg] 9400#0: bind() to 0.0.0.0:80 failed (98: Address already in use)
2015/03/14 08:36:42 [emerg] 9400#0: bind() to 0.0.0.0:80 failed (98: Address already in use)
2015/03/14 08:36:42 [emerg] 9400#0: bind() to 0.0.0.0:80 failed (98: Address already in use)
2015/03/14 08:36:42 [emerg] 9400#0: bind() to 0.0.0.0:80 failed (98: Address already in use)
2015/03/14 08:36:42 [emerg] 9400#0: bind() to 0.0.0.0:80 failed (98: Address already in use)
2015/03/14 08:36:42 [emerg] 9400#0: still could not bind()

I only have one config loading in sites-enabled. When I run:

$ grep -slir "listen 80"
$ sites-available/default

It shows that the default config has listen 80, but that shouldn't matter since it's not in sites-enabled.

$ ps ax -o pid,ppid,%cpu,vsz,wchan,command|egrep '(nginx|PID)'
  PID  PPID %CPU    VSZ WCHAN  COMMAND
 9468     1  0.0  97188 sigsus nginx: master process /usr/sbin/nginx
 9471  9468  0.0  97328 ep_pol nginx: worker process
 9472  9468  0.0  97368 ep_pol nginx: worker process
 9693  9641  0.0   9448 pipe_w egrep --color=auto (nginx|PID)

Here's a netstat showing what ports are being used:

$ netstat -tulpn

Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN      1300/master
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN      9468/nginx
tcp        0      0 0.0.0.0:2812            0.0.0.0:*               LISTEN      5980/monit
tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN      1174/mysqld
tcp        0      0 127.0.0.1:11211         0.0.0.0:*               LISTEN      1155/memcached
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      9468/nginx
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      1113/sshd
tcp6       0      0 :::25                   :::*                    LISTEN      1300/master
tcp6       0      0 :::9000                 :::*                    LISTEN      9106/hhvm
tcp6       0      0 :::22                   :::*                    LISTEN      1113/sshd
udp        0      0 127.0.0.1:11211         0.0.0.0:*                           1155/memcached

And here is my complete config in sites-enabled (the only one in there):

server {
    listen                  443 ssl default_server;

    limit_conn              gulag 15;
    server_name             www.my-website.com;

    access_log              /home/my-website/logs/access.log;
    error_log               /home/my-website/logs/error.log info;

    root                    /home/my-website/web;
    index                   index.php index.html;

    ssl_certificate /etc/nginx/ssl/my-website.com.chained.crt;
    ssl_certificate_key /etc/nginx/ssl/my-website.com.key;
    ssl_prefer_server_ciphers On;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    ssl_ciphers ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS;

    include                 /etc/nginx/includes/my-website_redirects_https.inc;
    include                 /etc/nginx/includes/file_cache.inc;
    include                 /etc/nginx/includes/wordpress.inc;
}

server {
    listen                  80;
    server_name             my-website.com www.my-website.com;
    return                  301 https://$server_name$request_uri;
}

server {
    listen                  443;
    server_name             my-website.com;
    return                  301 https://www.$server_name$request_uri;
}

server {
    server_name
        some-other-website1.com         www.some-other-website1.com
        some-other-website2.com         www.some-other-website2.com
        some-other-website3.com         www.some-other-website3.com
        some-other-website4.com         www.some-other-website4.com
        some-other-website5.com         www.some-other-website5.com

    rewrite ^(.*)$ https://www.my-website.com/some/page/ permanent;
}

server {
    server_name
        some-other-website6.com         www.some-other-website6.com
        some-other-website7.com         www.some-other-website7.com
        some-other-website8.com         www.some-other-website8.com

    rewrite ^(.*)$ https://www.my-website.com/some/other/page/ permanent;
}

server {
    server_name     subdomain.my-website.com;

    rewrite ^(.*)$ https://some.otherwebsite.com/ permanent;
}

server {
    server_name
        some-other-website9.com         www.some-other-website9.com
        some-other-website10.com         www.some-other-website10.com
        some-other-website11.com         www.some-other-website11.com

    rewrite ^(.*)$  https://www.my-website.com/ permanent;
}

I'm wondering if this bind() error is happening because of my config. Any ideas what I might be doing wrong? I'm using nginx/1.4.6 (Ubuntu). Any help would be greatly appreciated.