The server is now on a build that allows everyone on the 1.7.2 client to log into the server. If you are still using the old client, you will need to update to 1.7.2. Most of the new features do not work, but logging in will be much easier now. Use the tutorial in the previous post to update, but use the option for "Use Latest Version" instead of 1.6.4.
Thanks for your patience,