Well, apparently several people don't follow instructions or pay attention to the Forums. If you are one of them, and updated your minecraft to the 1.6.x , you probably already know you cannot access our server with that!!
We will NOT be upgrading the server until a stable Craftbukkit is in place. They are still waiting for minecraft to update to a stable enough version. If you've been following that, you know that Minecraft 1.6 has many bugs and crashes frequently, so needs to become more stable!!
To access WolfCraft servers again, what you need to do to downgrade back to the 1.5.x version of minecraft. What you need to do is to replace your /bin folder in the .minecraft folders. If you don't have a backup of that folder, let me know by sending me a PM and your email address and I can send you a copy of that folder that you will need to place into your .minecraft folder. And after that, DO NOT update the game, by selecting "NOT NOW" option when you login to minecraft. Once we upgrade the server, then you can upgrade your client!!