LONDON – President Barack Obama has arrived at Buckingham Palace for a private meeting with Queen Elizabeth II. Several thousand well-wishers crowded the traffic circle in front of the gated palace on Wednesday to cheer and wave as the limousine carrying Obama and first lady Michelle Obama rolled past. On the eve of a global economic summit, Obama promised world leaders he would listen, not lecture, as they seek a common fix to the financial crisis. "We can only meet this challenge together," he said Wednesday as the U.S. and Russia spoke on the summit sidelines about nuclear warhead reduction....