The Pick and Place Autonomous Demo, tabletop detection failed with error NO_TABLE, trying again

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After the following steps I got the above error, robot can move its arm but can not detect table and object. I use the remote database,ubuntu 11.04 64 bit electric ros. 1. export ROS_MASTER_URI=http://localhost:11311 export ROBOT=sim 2. roslaunch pr2_gazebo pr2_empty_world.launch 3. rosrun gazebo spawn_model -urdf -file table.urdf -model table -x 1.0 -y 0.5 -z 0.3 4.rosrun gazebo spawn_model -gazebo -file rospack find gazebo_worlds/objects/coffee_cup.model -model coffee_cup -x 1.2 -z 1 5. roslaunch pr2_tabletop_manipulation_launch pr2_tabletop_manipulation.launch 6. rosrun pr2_pick_and_place_demos pick_and_place_demo.py 7. input start or d enter det to detach the object in the gripper q to quit press enter to continue d [INFO] [WallTime: 1329522623.706395] [811.514000] detecting objects [INFO] [WallTime: 1329522623.706753] [811.514000] calling tabletop detection [ERROR] [WallTime: 1329522624.229342] [811.621000] tabletop detection failed with error NO_TABLE, trying again [ERROR] [WallTime: 1329522624.584169] [811.659000] tabletop detection failed with error NO_TABLE, trying again [ERROR] [WallTime: 1329522624.986114] [811.751000] tabletop detection failed with error NO_TABLE, trying again [ERROR] [WallTime: 1329522624.986445] [811.751000] tabletop detection failed too many times. Returning. type: