I don't know the specifics and SGB probably fear further repercussions if they say too much so we may never know. I believe they were audited and then told they had an outstanding tax-obligation for previous sales of the Series Of Dissent. I don't know if/how they resolved it, but they closed the doors in response to the ATO ruling.
RE: South Gippsland Bullion : Killed By The Australian Tax Office For Dissent?