It won't work if you're not using the latest Tekkit:
1. Download Tekkit: http://www.technicpack.net/tekkit/
2. Open it and select Tekkit from the dropdown. Not Technic or Vanilla. You want Tekkit.
3. Click on Options (underneath login button) and select 'Always use development builds'.
4. Log in and put in my server details: 184.108.40.206:25614
As of the new Tekkit 3.1.2 update, you can only get into our server by going to Options > Manual Select > 3.1.1 and selecting Yes when it asks you to update. Hopefully Tekkit will fix their 3.1.2 update soon.