Wait until a week before the show and check again. If that fails, check the day of. Ticketmaster holds tickets for guest lists and what not...if no one claims them, they go back to general public. A buddy of min bought his ticket 30 mins before the show and was seated right behind Gwenyth.
Its the same for hockey, every team releases league holds every Monday.
May 28/07 - The Police
March 30/08 - Foo Fighters
July 27/08 - Coldplay, Jay-Z - Pemberton Festival!
June 20+21/09 - Coldplay w/ Snow Patrol - Live 2009?
September 25/09 - Pearl Jam w/ Ben Harper
October 14/09 - Rob Thomas
October 28/09 - U2
April 1/10 - John Mayer
September 25/11 - Pearl Jam!