It could be your ISP doing it. Even though there are many many legitimate purposes for torrents (linux distributions namely), many ISPs frown upon it and block the standard ports. You could try using a different port. Also, with the amount of concurrent connections, many routers have problems keeping up, and you effectively get yourself DDoS'ed. you can try updating your router's firmware if you are using one. You could also try setting the max amount of connections to a lower number.