When I make a world with a layer of pistons, a solid block, and then pressure plates, then, when I land on a pressure plate...
It crashes! It works with one piston, one block, and a pressure plate, but not with a whole world of 'em. It worked in 1.5.1, but now it crashes.Here's the preset: 2;7,2x3,33:6,2,70(or)72;1;

What I expected to happen was...:
Every time I step on a pressure plate the block underneth it would raise up

What actually happened was...:
It loaded passed the building tarrian part, then it would be black for a short time; Sometimes, it would show a short view of the world, then it would crash.

Steps to Reproduce:
1. Go to "create new world, then go to "more world options".
2. Then go to superflat customization
3. And put in the above preset.Feel free to add some air and glass above the pressure plates. Then start the world, step on a pressure plate. Or use a spawn egg to make another mob step on it. It will still crash.

If you can fix this, THAN YOU DESERVE A BIG THANK YOU! BECAUSE THIS IS ONE OF MY FAVORITE PRESETS! THANK YOU!