Hi,
Are you using the latest version of HikaShop ?
We had actually changed the australia post plugin in order to get the full error message and not just the first word in a previous version of HikaShop.
Since you just have the first word it would indicate that either the modification we did was not enough or that you don't have the latest version.
If that's the case, then could you change the line:
if(preg_match_all('#([a-z_]+)=([a-z_\.0-9 ]+?)#Ui',$response,$matches)){
to:
if(preg_match_all('#([a-z_]+)=(.*)#Ui',$response,$matches)){
in the file plugins/hikashopshipping/aupost.php and try again ?