Minecraft Crashes every few steps I take

I was walking in my Hardcore world's village, when Minecraft crashed for no obvious reason. This happened again, after which I reverted back to 1.4.2 and the problem seems to have stopped on this version.

What I expected to happen was...:
Me to walk more than 10 blocks

What actually happened was...:
I walked ~10 blocks and Minecraft crashed. Twice.

Steps to Reproduce:
I'm not entirely sure how to reproduce this. If required, I can send you the world save and the rough co-ordinates of the area? I've attached the first crash report it gave me, presuming the second is the same.