rosserial error when publishing IMU data

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I get the following error when I try to use an Arduino to publish data from an IMU:

balto@T510:~$ rosrun rosserial_python serial_node.py /dev/ttyUSB0
    [INFO] [WallTime: 1364421432.288265] ROS Serial Python Node
    [INFO] [WallTime: 1364421432.288485] Connecting to /dev/ttyUSB0 at 57600 baud
    Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
    Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
    Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
    Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
    Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
    Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
    Exception AttributeError: AttributeError("'_DummyThread' object has no attribute '_Thread__block'",) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored
    [INFO] [WallTime: 1364421434.987086] Note: publish buffer size is 512 bytes
    [INFO] [WallTime: 1364421434.987635] Setup publisher on /imu/data [sensor_msgs/Imu]
    Traceback (most recent call last):
      File "/home/balto/catkin_ws/install/lib/rosserial_python/serial_node.py", line 79, in <module>
        client.run()
      File "/home/balto/catkin_ws/install/lib/python2.7/dist-packages/rosserial_python/SerialClient.py", line 393, in run
        self.callbacks[topic_id](msg)
      File "/home/balto/catkin_ws/install/lib/python2.7/dist-packages/rosserial_python/SerialClient.py", line 99, in handlePacket
        m.deserialize(data)
      File "/opt/ros/groovy/lib/python2.7/dist-packages/sensor_msgs/msg/_Imu.py", line 196, in deserialize
        raise genpy.DeserializationError(e) #most likely buffer underfill
    genpy.message.DeserializationError: unpack requires a string argument of length 72

Any ideas what would cause this error? Thank you in advanced.