When Placing a sign you get kicked for malaformed JSON

I just updated my SMP server (with world resetted) to 15w31a as we always kept with the snapshots, although when I (The Owner) placed a sign I instantly got kicked, can no longer join the server at that and received an error: (Screen Shot below)
http://i.imgur.com/cR2znzF.png

Internal Exception: io.netty.handler.codec.DecoderException:
com.google.gson.JsonSyntaxException:
com.google.gson.stream.MalaformedJsonException: Use JsonReader.setLenient(true) to accept malaformed JSON at line 1 column 2