question regarding BIND and "zero ttl"

[Christian Hammers <ch@westend.com>]

Hello 

One of our cron scripts regularily says 
>  !!! hostname-xyz.westend.com A record has zero ttl
on stderr. A prepended "killall -INT named" in the crontab shows
that at this time there is no entry in the bind cache for this host
because the 86400s of the TTL are expired and bind cleared it.
So far so good, but why doesn't bind simply request the information 
from upstream. It has no forwarders installed and the authoritative hosts
of course always say TTL 86400 (just checked both of them).

Does anybody know a reason? We always get the error with this host with the
"host_20000331-1.deb" on "bind_1:8.2.4-1.deb". 

thanks,

-christian-