基于和这个问题，我建议你检查一下你没有运行任何防火墙或端口阻塞软件（比如PeerGaurdian），并且你没有在任何地方阻止Amazon / EC2你的系统。

Based on this question and this question, I'd suggest you check that you don't have any firewall or port blocking software running (like PeerGaurdian) and that you're nto blocking Amazon/EC2 anywhere on your system.