*** Due to disappointing ticket sales, the country-pop trio is postponing as many as half the 42 dates announced for their coming "Accidents and Accusations" concert tour, which starts July 21. After playing 11 U.S. shows, the Chicks will for the moment steer clear of cities like St. Louis, Los Angeles and Jacksonville, Fla. *** It isn't clear that any one factor has caused the trio's recent problems, but there are plenty of candidates. The conventional wisdom has held that they were hurt by lead singer Natalie Maines's 2003 comments to a British audience that the band was "ashamed" that...