Ubuntu :: External Machines Can See Some Subdomains But Not All

I have a DNS server on my LAN at 192.168.140.25. Going by the example in the O'Reilly DNS and BIND book I bought, I set up the domain movie.edu and toystory.movie.edu. To my great surprise and delight, I can access toystory.movie.edu in a browser from another PC on the LAN (as long as I add 192.168.140.25 to the DNS servers). Encouraged by this victory, I decided to try to set up another subdomain at coupon.movie.edu. This kind of worked but not completely. Interestingly, I can get to both toystory.movie.edu and coupon.movie.edu on my server, but on my PC, I can only get to toystory.movie.edu, not coupon.movie.edu.

Here is my db.movie.edu:
Code:
$TTL 3h
movie.edu. IN SOA toystory.movie.edu. al.movie.edu. (
1 ; Serial
3h ; Refresh after 3 hours
1h ; Retry after 1 hour
1w ; Expire after 1 week
1h ) ; Negative caching TTL of 1 hour

movie.edu. IN NS toystory.movie.edu.
movie.edu. IN NS coupon.movie.edu.
;
; Host addresses
;
localhost.movie.edu. IN A 127.0.0.1
toystory.movie.edu. IN A 192.168.140.25
coupon.movie.edu. IN A 192.168.140.25

And here is my named.conf:
Code:
options {
directory "/etc/bind";
};

zone "movie.edu" in {
type master;
file "db.movie.edu";
};

zone "140.168.192.in-addr.arpa" in {
type master;
file "db.192.168.140";
};

zone "0.0.127.in-addr.arpa" in {
type master;
file "db.127.0.0";
};

zone "." in {
type hint;
file "db.cache";
};

#include "/etc/bind/named.conf.options";
include "/etc/bind/named.conf.local";
#include "/etc/bind/named.conf.default-zones";