rosrun turtlesim turtlesim_node segmentation fault / rqt ImportError

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I am new to ROS. I am working through the beginner's tutorials. Version: ROS Indigo, OS Kubuntu 14.04. I was trying rosrun turtlesim turtlesim_node and the result was: Segmentation fault ( core dumped). Also I was trying to run rqt and the result was:

Traceback (most recent call last):
File "/opt/ros/indigo/bin/rqt", line 13, in <module>
sys.exit(main.main())
File "/opt/ros/indigo/lib/python2.7/dist-packages/rqt_gui/main.py", line 59, in main
return super(Main, self).main(argv, standalone=standalone, plugin_argument_provider=plugin_argument_provider, plugin_manager_settings_prefix=str(hash(os.environ['ROS_PACKAGE_PATH'])))
File "/opt/ros/indigo/lib/python2.7/dist-packages/qt_gui/main.py", line 336, in main
from python_qt_binding import QT_BINDING
File "/opt/ros/indigo/lib/python2.7/dist-packages/python_qt_binding/__init__.py", line 55, in <module>
from .binding_helper import loadUi, QT_BINDING, QT_BINDING_MODULES, QT_BINDING_VERSION # @UnusedImport
File "/opt/ros/indigo/lib/python2.7/dist-packages/python_qt_binding/binding_helper.py", line 267, in <module>
getattr(sys, 'SELECT_QT_BINDING_ORDER', None),
File "/opt/ros/indigo/lib/python2.7/dist-packages/python_qt_binding/binding_helper.py", line 95, in _select_qt_binding
raise ImportError("Could not find Qt binding (looked for: %s):\n%s" % (', '.join(["'%s'" % b for b in binding_order]), '\n'.join(error_msgs)))
ImportError: Could not find Qt binding (looked for: 'pyqt', 'pyside'):
ImportError for 'pyqt': /usr/lib/python2.7/dist-packages/PyQt4/QtCore.so: undefined symbol: _ZTI13QStateMachine
ImportError for 'pyside': /usr/lib/x86_64-linux-gnu/libpyside-python2.7.so.1.2: undefined symbol: _Z9qBadAllocv

What can I do? Thanks in advance.