I was working on my witch farm when i noticed that some redstone blocks were missing. There were also some strange hitboxes left behind. When I looked at it with MC-Edit, I saw that they were block 36's. But they are incomplete blocks, they have no tile entity associated.
Please upload the world so that we can investigate waht could probably causing the problem.
Also, please force a crash by pressing F3 + C for 10 seconds while in-game and attach the crash report (
[minecraft|http://hopper.minecraft.net/help/finding-minecraft-data-folder]/crash-reports/crash-<DATE>-client.txt
) here.