[turtle_pointer-6] process has died when running tf tutorial

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I tried to follow the tutorial from here :

http://www.ros.org/wiki/tf/Tutorials/Introduction%20to%20tf

But there's some error and a process died. This is the full message :

roslaunch turtle_tf turtle_tf_demo.launch 
... logging to /home/albert/.ros/log/52b0e6d8-1099-11e2-aceb-5404a6dc3a5e/roslaunch-Albert-PC-11357.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://Albert-PC:50707/

SUMMARY
========

PARAMETERS
 * /rosdistro
 * /rosversion
 * /scale_angular
 * /scale_linear
 * /turtle1_tf_broadcaster/turtle
 * /turtle2_tf_broadcaster/turtle

NODES
  /
    sim (turtlesim/turtlesim_node)
    teleop (turtlesim/turtle_teleop_key)
    turtle1_tf_broadcaster (turtle_tf/turtle_tf_broadcaster.py)
    turtle2_tf_broadcaster (turtle_tf/turtle_tf_broadcaster.py)
    turtle_pointer (turtle_tf/turtle_tf_listener.py)

auto-starting new master
Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
process[master]: started with pid [11373]
ROS_MASTER_URI=http://localhost:11311

setting /run_id to 52b0e6d8-1099-11e2-aceb-5404a6dc3a5e
Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
process[rosout-1]: started with pid [11386]
started core service [/rosout]
Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
process[sim-2]: started with pid [11398]
Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
process[teleop-3]: started with pid [11415]
Reading from keyboard
---------------------------
Use arrow keys to move the turtle.
Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
process[turtle1_tf_broadcaster-4]: started with pid [11446]
Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
process[turtle2_tf_broadcaster-5]: started with pid [11447]
Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
process[turtle_pointer-6]: started with pid [11448]
Traceback (most recent call last):
  File "/opt/ros/fuerte/stacks/geometry_tutorials/turtle_tf/nodes/turtle_tf_listener.py", line 57, in <module>
    (trans,rot) = listener.lookupTransform('/turtle2', '/turtle1', rospy.Time())
tf.ExtrapolationException: Lookup would require extrapolation at time 1349626149.653091908, but only time 1349626149.653103113 is in the buffer, when looking up transform from frame [/turtle1] to frame [/turtle2]
[WARN] [WallTime: 1349626149.680432] Inbound TCP/IP connection failed: connection from sender terminated before handshake header received. 0 bytes were received. Please check sender for additional details.
[turtle_pointer-6] process has died [pid 11448, exit code 1, cmd /opt/ros/fuerte/stacks/geometry_tutorials/turtle_tf/nodes/turtle_tf_listener.py __name:=turtle_pointer __log:=/home/albert/.ros/log/52b0e6d8-1099-11e2-aceb-5404a6dc3a5e/turtle_pointer-6.log].
log file: /home/albert/.ros/log/52b0e6d8-1099-11e2-aceb-5404a6dc3a5e/turtle_pointer-6*.log

How to solve this problem? Thanks~