The Lakers were halfway to a series problem tonight in Game 2 of their second-round playoff series against the Dallas Mavericks. They did a good many things right in the first half, but they couldn’t stop Dirk Nowitzki and they couldn’t build any momentum. Kobe Bryant and Andrew Bynum each scored 14 points. Nowitzki had 15. Ron Artest began to guard Nowitzki late in the half and muscled him more than Pau Gasol or Lamar Odom.