No resolving in some geographic areas

[Carlos Alberto Bernat Orozco]

Hi Group
I need help for a question which is killing me!! I configured BIND 8 on
CentOS for my web site and BIND resolves fine for some users but doesn't in
other cities.

this the result for dig:
# dig myhost.myserver.com.co

; <<>> DiG 9.3.2 <<>> myhost.myserver.com.co
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1916
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 6, ADDITIONAL: 4

;; QUESTION SECTION:
;myhost.myserver.com.co.          IN      A

;; ANSWER SECTION:
myhost.myserver.com.co.   7244    IN      A       xxxx.xxxx.xxxx.xxxx

;; AUTHORITY SECTION:
co.                     45247   IN      NS      cmcl2.nyu.edu.
co.                     45247   IN      NS      saell.cc.columbia.edu.
co.                     45247   IN      NS      cdcnet.uniandes.edu.co.
co.                     45247   IN      NS      kenshin.uniandes.edu.co.
co.                     45247   IN      NS      mintaka.uniandes.edu.co.
co.                     45247   IN      NS      ayax.uniandes.edu.co.

;; ADDITIONAL SECTION:
ayax.uniandes.edu.co.   177     IN      A       157.253.50.3
cdcnet.uniandes.edu.co. 177     IN      A       157.253.1.13
kenshin.uniandes.edu.co. 177    IN      A       200.57.34.101
mintaka.uniandes.edu.co. 177    IN      A       200.31.69.106

;; Query time: 40 msec
;; SERVER: xxxx.xxxx.xxxx.xxxx#53(xxxx.xxxx.xxxx.xxxx)
;; WHEN: Wed Jul  4 20:38:46 2007
;; MSG SIZE  rcvd: 274



Where could be the error?? Is a problem of the foreign ISP of my clients??

Please help and thanks in advanced!!!

Carlos Bernat