Starting from 2.78, the old basic rigify Human is not generated correctly anymore.
Problem: fk bones both on legs and arms have 0 length in pose mode. Because of this fk/ik/fk snaps raise errors. Rest Pose and Edit mode look ok though.
The problem seems unrelated to code previously commited on rigify. The current version of the addon was tested on 2.77 and it works without flaws.
Steps to reproduce:
In 2.78c create a Human (meta-rig), hit generate