Zone update refused:
184.108.40.206 (domain.com.au/IN): 58 Time(s)
Well, it means that a zone update was not authorized.
I would need to know more details though as to whether this was an outbound or inbound zone update.
Normally in a correct bind configuration only the master nameservers of a zone (domain) are authorized to do zone updates. Of course there is dynDNS but I will not go into that here. The there is the zone update that occurs between the Master and its Secondaries by either sending a notify and the Secondaries comparing serial no. for the zone and the update checks depending on the time out value for the secondaries in the zone.
Sometimes people like to inject false DNS information into an unprotected zone to hijack it though!
So what I would need to see is the zone file for that zone in question and the part of the bind log file where it states the error. You can send it through PM if you like and I can then post the solution here to keep information private.