A man was arrested in the lobby of a downtown hotel where Sen. Hillary Rodham Clinton was speaking after police determined he'd failed to register as a sex offender. Ransom T. Rowe, 33, of Melrose, Mass., approached security guards at the Boston Park Plaza hotel on Thursday, asking if Clinton was speaking there. He told the guard that he had sent e-mails to the former first lady, now New York's junior senator. The guard alerted state police, who checked Rowe's records and found an outstanding warrant for failing to enter his name and address with the state's sex offender registry,...