Powell Cancels Greece Visit Amid Protests ATHENS, Greece - Secretary of State Colin Powell on Saturday canceled a weekend visit to attend the closing ceremony of the Olympics just hours after demonstrators staged a protest march in central Athens.    Greece's foreign ministry said that Powell informed his Greek counterpart, Petros Moliviatis, that "urgent responsibilities" prevented him from carrying out the visit - which was to include meetings with Premier Costas Caramanlis and U.S...