Master Server replies, but nothing will connect

[jamz]

1Cap, I can only block connections to the master server. If a player has the server list, but can't connect to any of the servers, it's a problem with his/her network or ISP.

This isn't the first time this problem has come up:
http://forum.cubers.net/thread-5684.html
http://forum.cubers.net/thread-5506.html
http://forum.cubers.net/thread-2936.html