The IMF 400 tonnes gold sale story has been floating around for over 2.5 years: http://www.321gold.com/editorials/phillips/phillips020807.html
Even if it does eventually happen there were gold sales by the IMF over the gold bull in the late 70s, it was a lot more being sold and didn't keep the price down:
******************************* Auctions and "restitution" sales (1976-80). The IMF sold approximately one-third or 1,555 tonnes of gold (50 million ounces) of its then-existing gold holdings following an agreement by its members to reduce the role of gold in the international monetary system. ******************************* http://goldnews.bullionvault.com/IMF_past_sales
