I don't know what to tell you... to the best of my knowledge there's absolutely no way for my code to kick off the entire test suite -- I always do that through PyDev (which doesn't cause the bug, by the way). The closest thing is the boilerplate at the bottom of every test file:

if __name__ == "__main__":
    unittest.main()

...but even that would only start the tests in that file, not the entire suite.

Another thing that makes me think multiprocessing is re-running the original command line is that if I use "python setup.py test" to start the tests, when it gets to the MP tests it seems to run that command for each Process that gets started, but if I use "nosetests", it seems to run "nosetests" for each started Process.