MC crashing when updating texturepack in

i was making my texturepack... and i updated an already in use texturepack, like i use to be able to do before 13w09a/b.

Steps to re-produce error...

Select texturepack and load a world.

go into texturepack selection menu in-game. and leave it open.

copy texturepack.zip to desktop and edit a texture.

copy back the edited file to the mc texture folder.

game crashes, as soon as used file is updated...

(it never use to do this before 13w09a/b)