Tornado应用无法启动

继杯具的mysql后Tornado也出问题了。
应用都无法启动，自带最基本的helloword.py
$ python helloword.py
无反应…… 这是什么情况。访问应用也是空白。只能Ctrl+c退出

^CTraceback (most recent call last):
File "helloworld.py", line 43, in <module>
main()
File "helloworld.py", line 39, in main
tornado.ioloop.IOLoop.instance().start()
File "/Library/Python/2.7/site-packages/tornado-2.1-py2.7.egg/tornado/ioloop.py", line 283, in start
event_pairs = self._impl.poll(poll_timeout)
File "/Library/Python/2.7/site-packages/tornado-2.1-py2.7.egg/tornado/ioloop.py", line 552, in poll
kevents = self._kqueue.control(None, 1000, timeout)
KeyboardInterrupt