So I finally traced my MSN disconnect problem to my router. Turned out my model, the DI-524 has been known to overheat when handling too many connections. And to make matters worst, I was stressing it out by running custom firmware on it - yes, the same one I recommended to use in a previous blog post...

I've solved the problem temporarily by reverting to factory firmware and taking the cover off the router to allow for more airflow.