No subject

>The delegation in the 'tau.trelleborg.com' zone appears to be correct -
>this is confirmed by the fact that the server I am querying is trying to
>ask the name servers of the bre.tau.trelleborg.com zone to resolve the
>query!

You need an A record for bre.tau.trelleborg.com in the parent domain.  This
is called a "glue record", and it's needed whenever the subdomain's
nameserver is in that subdomain.

--
Barry Margolin, barmar at genuity.net
Genuity, Woburn, MA