Getting "unapproved update from" slave servers

[Guy Lancaster]

  I'm fairly new to setting up DNS servers.  I'm running
Bind 8.2.6 on Redhat 6.0 on 3 machines.  Everything seemed
fine for a few days and then today in the master server's
log messages I'm getting "unapproved update from" the slave
name servers on several zones.

  I should only be getting requests for serial numbers and
zone transfers from the slaves.  What's happening?

  I am using allow-query and allow-transfer clauses in my
named.conf files.  All of these include the addresses for
the master server.

  Thanks in advance.

            Guy