> 	Hi.  I have a long-running named running on our mail server as a
> caching name server.  (This is Under NetBSD 1.2G with sources as of
> September 1 1997 or so.)  The named is 4.9.3-P1.

You shouldn't run such old named code.  There have been many
security-related and other bug fixes since 4.9.3.  Some of those fixes are
intended to make it less likely that the cache gets corrupted in the way
that you seem to be experiencing. 

Please upgrade to a newer version of named.  I recommend the latest 8.1.2
release.  See http://www.isc.org/bind.html.

--apb (Alan Barrett)