My operating system is windows 7. Java Version: 1.6.0_24. I used the pick block button to get a one of the new red sandstone slabs, the game crashed almost immediatly. I went back in to test if it had to do with the slab. I pressed the middle mouse wheel and it crashed again. The slab was on top of normal sandstone because it was a redstone ready world, and there was a normal sandstone slab above for side-by-side comparison. i went back in again and pick blocked the other red sandstone things and it didnt crash. i placed a another red sandstone block somewhere else to make sure it wasnt the location or the normal sandstone slab that was above the first one and it still crashed, every time almost instantly.