The company distributing a new documentary about the Dixie Chicks has blasted the NBC and CW networks for allegedly refusing to accept a commercial spot for the film, which opens in four theaters Friday. In a press release issued late Thursday, the Weinstein Co. said NBC rejected a spot for "Shut Up and Sing," because the spot included material that "disparages President Bush." The film, playing initially in Los Angeles and New York, revolves around the political firestorm stirred up in 2003 when the Dixie Chicks criticized Bush during a concert in London. Nicole Sperling and Kimberly Nordyke report.