To diagnose the access violation, it may help if you install the debug binaries and try to reproduce the crash using python_d.exe. Attach the dump file to this issue.

Regarding the multiprocessing question, if its a separate issue you need to file it on its own and nosy davin. At first glance, I don't see why the handle is None in the lock's __exit__ method. After you acquire the lock, try logging the connection information. For example:

    import multiprocessing as mp
    import multiprocessing.util

    def test(lock):
        with lock:
            mp.util.info('test:lock:token: %r' % (lock._token,))
            mp.util.info('test:lock:handle: %r' % (lock._tls.connection._handle,))

    if __name__ == '__main__':
        mp.util.log_to_stderr(mp.util.INFO)
        lock = mp.Manager().Lock()
        p = mp.Process(target=test, args=(lock,))
        p.start()
        p.join()