Bill Clinton is never at a loss for company. When he's not globe-trotting or charming audiences for as much as $400,000 a speech, he's often schmoozing visitors in his suite of offices in Harlem. Last July, the former president sat down with a billionaire impressed with the William J. Clinton Foundation's campaign against AIDS in Africa. The two men chatted amiably over lunch for more than two hours, and the visitor pledged to write Clinton's foundation a generous check. But there was something unusual, if not plain weird, about the meeting. NEWSWEEK has learned that the billionaire so eager to...