happening since R4. 1.2.3 1.2.4 I updated my client and everything. Tried the dev builds, but it says outdated server.
Is your server updated to 1.2.3 or 1.2.4? I can send you a link of a Minecraft down grader if this is any consolation? http://www.youtube.com/watch?v=aAGGdpAle4E