Multiplayer Glitch

I have a map which works in singleplayer but not multiplayer. This started when I started my map in the newest snapshot, but it doesn't seem to be a snapshot problem (other people in 1.8.7 have had this problem pre-snapshot). It gives me this error:
Internal Exception: io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerIndex(9) +
(next line)
length(1) exceeds writerIndex(9): UnpooledHeapByteBuf(ridx: 9, widx: 9, cap: 9}