I don't know if this might be causing your problem, but most socket implementations use quite a big buffer for incoming data by default. I had a lot of trouble with another real-time networked application until I realised this. Reducing this buffer to the minimum helped a lot in my case. Also, I would strongly recommend using UDP instead of TCP.
BTW, does anyone know if any good bibliography about real-time networked games, or real-time networked general applications? -- http://mail.python.org/mailman/listinfo/python-list
