error (no valid DS)

[Agustín Dixan Díaz Corrales]

hi list, looking a syslog a bind9 log i note these:
error (no valid DS) resolving 'www.domain.cu/A/IN': ISP_IP_DNS#53

when i try to access from my localnet to any place of this domain 
(www.domain.cu), bind dont resolv the consult....the forward dns ip from 
my isp are declared but in specific rang of ip in my networks bind dont 
resolv it....any idea?

thanks