Can't Enter a World (Single and Mulitplayer!) / Ticking Screen - Fixed

No Mods or Stuff, just the normal Version of Minecraft was used!

What I expected to happen was...:
Join my updated server (1.7.2 -> 1.7.9 R2 Craftbukkit) and play a bit.

What actually happened was...:
I joined but i could not enter the world. It kicked me out in the loading screen.
"Joining" disapears and CRASH.

Steps to Reproduce:
1. Use Version 1.7.9 or 1.7.10
2. Start the Game
3. Choice a SIngleplayer world or Multiplayerserver
4. Join it
5. Get the Crash