Hi mojang team, here is a bug from the 1.8.1 pre 5, when i created the new world, i walked in east direction, i found this (sorry for my bad english), and i waited for 3 minutes and nothings happen with this chunks (around 4 chunks affected).
Environment
Windows 7 32 bits, Intel Celeron Dual Core @ 1.60 GHz, Java version 7 update 71, Graphic Card: NVIDIA GT520 1G DDR3 2G DDR3, drivers version 344.75...
Looks like
MC-2545
or
MC-62958