Have had exactly the same problem. My Server is located at home with a 150mps/10mps' eventhough the ping was by 200-250ms. The two dedicated Server were installed on a windows 7 machine connected to a performant router. After migrating the server to a virtual machine with ubuntu(with a dedicated network card) i finally get a ping of max 10ms, i asked many players about their ping, result max 40ms. I think that the problem resides in the Windows TCPIP Stack and some optimization Algorithm that rise the ping.