Severe Multiplayer Error

As I joined my multiplayer server after the snapshot release, I was on for around half a second and then lost connection with the error code below.
Details:
When I spawned into the server I was in the water in the lake with the town around it. The town contains several different blocks and entities, like for example nether portal, signs, item frames, villagers etc, so thus I can't track down what exactly what is the issue. I loaded up a world in singleplayer and it didn't do anything, works just fine.
-Brix