The [U.S.] National Labor Relations Board has filed a complaint accusing Wal-Mart of unfair labor practices against meat cutters who voted to create Wal-Mart's first unionized U.S. labor group in Jacksonville last year. Wal-Mart threatened employees, interrogated them about their union sympathies and fired pro-union workers, according to the complaint, signed last month by Curtis Wells, regional director in the NLRB's Fort Worth office.