Australia Post works fine in the latest version. Presume you haven't properly configured Australia Post or your products (such values as weight, dimensions).
I have set it to "3167" ,it is correct post code in Australia, before I updated to 1.6 version, everything is ok, but Today after I update to version1.6, the shipping method , none of them can work, Austalia post, orderby weight, orderby total, none of them can work.