LONDON, Feb 3 - The dollar fell to a new three-year low against the yen on Tuesday following the news that poison ricin had been found in a U.S. Senate building. Also weighing on the dollar was speculation that the Group of Seven finance ministers meeting later this week would make no efforts in halting the dollar's slide. "The ricin and the budget announcement got the euro/dollar moving higher. The dollar's being sold aggressively across the board," said Aziz McMahon, currency strategist at ABN AMRO. The White House said on Monday it saw the budget deficit at $521 billion in fiscal year 2004, a reminder of one of the key driver of dollar weakness. By 0750 GMT the dollar hit a low of 105.32 yen , having fallen for the fourth consecutive session.//