crash on leaving nether

crash on loading overworld
What I expected to happen was...:
load and enter overworld

What actually happened was...:
game crash on loading

Steps to Reproduce:
1.updated from 13w37b while game saved in nether
2.entered portal to overworld
3.game crashes

everything works fine on return to 13w37b but can only load the nether on 13w38a through 38c any attempt to load overworld crashes the game