When I render a certain area on my map (on a server using 14w28a), which I presume is the area with all the command blocks, I get kicked from the game and get this message:
Connection Lost
Internal Exception: io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerIndex(506215) + length(282880) exceeds writerIndex(592487): UnpooledHeapByteBuf(ridx: 506215, widx: 592487, cap: 592487/592487)
Please attach the complete output of the "Development console" which can be found on the second tab of the launcher.
If the launcher closes after game start, please edit your profile and select "Launcher visibility" then, "Keep the launcher open".