BIND problems!

Hi,

I am using bind 8.4.1 (and it has happened on a previous version that
came precompieled with freebsd 4.9) where it sometimes cannot resolve
names on a certain server, it only happens with one specific server
(also running bind 8.4.1). It doesn't have any errors or warnings in
logs, when using nslookup it just gives the output of Non-existant
host/domain. As far as its aware the data its receiving is valid and
non-existant.

Does anyone have any ideas, i've upgraded all the servers involved and
checked the config, its the most basic config on the authoritive
server, I have many other servers configued in this way and it never
happens with them..

Any help or any known problems i don't know about

Thanks

Tom