Secret Service Investigating Alleged Bush Threat— WASHINGTON (Reuters) - The U.S. Secret Service said on Sunday it had no comment on a report that a trucker had been arrested outside Chattanooga, Tennessee after allegedly threatening President Bush. "The Secret Service is conducting an investigation and due to there being an active, ongoing investigation, I can't make any further comment about it," said a Secret Service official who spoke on condition of anonymity. Cable News Network reported the man told police he had a 3,000-pound bomb "... and the president has problems," in a telephone conversation that led to his apprehension...