The rumour has been around for a while but it seems to be true according to this report from Gamespot.
More information.Rumours were swirling late last week that Australia's strict games classification regime had struck its highest-profile victim for 2008, with Fallout 3 apparently being refused a rating. It seems the rumours were true, with confirmation coming tonight that Bethesda's upcoming post-apocalyptic action-RPG has indeed been banned for sale in Australia.
The most recent update for the Web site of Australia's Office of Film and Literature Classification (OFLC) shows that Fallout 3 has been refused classification. Unlike films or DVDs, the highest rating allowable for a game in Australia is MA 15+, which means any title that has content deemed unsuitable for a 15-year-old is illegal to sell or promote in this country.