This bug was found on random on a multi player server.

The bug consist out of crash client side (not server side)
When entering certain Chunk that are lined up in a bend like shape.
it causes huge FPS drops for all that are inside of those chunks.
Tp'ing them out restores there FPS.

after digging we found out it was caused by a single block.
this block was being moved from west to east.
the height of the block seems to unrelated.
Also when we removed the block but kept the redstone clock going, no lag was experienced.

a friend of my has 2 graphic cards and was able to "survive" the lag, he could still walk around but every time inside that area His fps drops like anyone else but not enough to freeze and crash him.

I also noticed in my console it keep saying: [Client thread/INFO]: Warning: Clientside chunk ticking took 2600 ms

we tested it to see if it also did this in singleplayer with different version and different seeds.
we tested it from 1.7.2 to the lastest snapshot

the newest snapshot only seems to move the "crashing Chunks"

to replicate this bug: I have included a world download. but also a video
and the forced crash log, but here the text version:

Goto. -128 54 112
place a block there. on the west side place a piston so it can retract to the block further west. put this piston a a timer, make sure the chunks are marked as spawn by using /setdefaultworldspawn. It is recommend to play a sound when the piston is moving to everyone you so know when it moves. Then Goto somewhere around -160 y 277 and find the chunks that cause to jitter every time you hear the sound.

The Video of me exploring this crash.
http://www.youtube.com/watch?v=MhhcGA6FAvM&feature=youtu.be