By DONNA ABU-NASR, Associated Press Writer , BEIRUT, Lebanon – Her voice brought together under one roof both supporters of the beleaguered government and opponents trying to topple it. Yet in this tense country, sharp disputes break out even at a performance by Fairouz, Lebanon’s premier diva and the star of a musical about a corrupt government. Last weekend’s three-night run of "Sah el-Nom," loosely translated as "A Good Night’s Sleep," was supposed to open an annual summer festival in the ancient city of Baalbek. Israel’s July-August offensive on Lebanon forced organizers to postpone until December, hoping that by then calm would prevail.But opening night coincided with a new crisis that many fear could tear apart the country