Error in mathjax_sage.js. What's wrong with my configuration?

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I have installed Sage 6.1 on a brand new laptop running Ubuntu 12.04 LTS. When I fired up Sage and tried opening a worksheet in the notebook (Chrome/Firefox), the inline latex equations did not compile (they just appear as $...$) and the display equations appeared correctly, but in the color green. In the JS console I get the error:

Failed to load resource: the server responded with a status of 500 (Internal Server Error) http://localhost:8080/javascript/dynamic/mathjax_sage.js

And here's the stack trace in Terminal:

Executing twistd  --pidfile="sage_notebook.sagenb/sagenb.pid" -ny "sage_notebook.sagenb/twistedconf.tac"
/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Crypto/Util/number.py:57: PowmInsecureWarning: Not using mpz_powm_sec.  You should rebuild using libgmp >= 5 to avoid timing attack vulnerability.
  _warn("Not using mpz_powm_sec.  You should rebuild using libgmp >= 5 to avoid timing attack vulnerability.", PowmInsecureWarning)
2014-02-10 19:07:46-0500 [-] Log opened.
2014-02-10 19:07:46-0500 [-] twistd 13.1.0 (/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/bin/python 2.7.5) starting up.
2014-02-10 19:07:46-0500 [-] reactor class: twisted.internet.epollreactor.EPollReactor.
2014-02-10 19:07:46-0500 [-] QuietSite starting on 8080
2014-02-10 19:07:46-0500 [-] Starting factory <__builtin__.QuietSite instance at 0x5ba97a0>
2014-02-10 19:07:50-0500 [-] WSGI application error
    Traceback (most recent call last):
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Twisted-13.1.0-py2.7-linux-x86_64.egg/twisted/python/threadpool.py", line 212, in _worker
        o = self.q.get()
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Twisted-13.1.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 118, in callWithContext
        return self.currentContext().callWithContext(ctx, func, *args, **kw)
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Twisted-13.1.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 83, in callWithContext
        self.contexts.pop()
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Twisted-13.1.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 340, in run
        self.started = True
    --- <exception caught here> ---
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Twisted-13.1.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 315, in run
        appIterator = self.application(self.environ, self.startResponse)
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1836, in __call__
        return self.wsgi_app(environ, start_response)
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1820, in wsgi_app
        response = self.make_response(self.handle_exception(e))
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1403, in handle_exception
        reraise(exc_type, exc_value, tb)
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1817, in wsgi_app
        response = self.full_dispatch_request()
      File "/home/corleymj/Programs/sage-6.1-x86_64-Linux/local/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1477, in full_dispatch_request
        rv = self ...