Bind Problem

Hi all,

I've 2 Debian Etch (4) box used as ns1 and ns2 with BIND9. My domain name is something like this:
subdomain.domain.com

And I've 2 authorized DNS servers for the subdomain. I set this line in both of ns1 and ns2 (I.e. in ns1.subdomain.domain.com and ns2.subdomain.domain.com):

cw                      A       188.88.88.88

This setting was set in /etc/bind/db.subdomain.domain.com .

The result of dig command was like this:

Command:

dig @ns1.subdomain.domain.com cw.subdomain.domain.com

Result:

; <<>> DiG 9.3.4-P1.1 <<>> @ns1.subdomain.domain.com cw.subdomain.domain.com
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49076
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4

;; QUESTION SECTION:
;cw.subdomain.domain.com.              IN      A

;; ANSWER SECTION:
cw.subdomain.domain.com.       86400   IN      A       188.88.88.88

dig showed the same result on ns2.subdomain.domain.com.
But when I sent the below query, I got nothing:
Command:

dig @ns1.domain.com cw.subdomain.domain.com

Result:

; <<>> DiG 9.3.4-P1.1 <<>> @ns1.domain.com cw.subdomain.domain.com
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 1182
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;cw.subdomain.domain.com.              IN      A

;; AUTHORITY SECTION:
subdomain.domain.com.          3600    IN      SOA     ns1.subdomain.domain.com. root.subdomain.domain.com. 2008012900 3600 900 1209600 3600

But there was no ANSWER section. I set these setting 2 or 3 days ago. My old *.subdomain.domain.com hasn't any problem.

Any idea to solve the problem?

..... I forgot to increase SOA.