Definitely no changes made by me to the site.
I have just checked again this morning and it is working again?!?
After my above post I went to the auspost edeliver website and registered.
http://www.edeliver.com.au/Templates/ifs/IFS_About_IFS.htm#Rate_Calculation
Maybe my site had been blocked as I wasn't previously registered? Might me worth a try for the OP.