I'm in Melbourne also. Funny, your Profile Local Time puts you 16 hours behind me!
I don't have any problem playing Ten HD, or any of the other channels that broadcast AC3.
There have been quite a few channel frequency and lineup changes over the last year or two. Maybe rescan your channels and see if the problem goes away. I rescanned a month or so back to pick up new channels and align with the OTA EPG again, after the EPG stopped making sense.