Ubuntu 14.04 x64
Broken: Blender 2.76 48f7dd6 (from blender.org)
- Open the file (it is in Armature Edit Mode and the armature parented to the wire-cube)
- Use the left panel to clear object's parent (Object Panel - Relations - Parent - click on the "X")
- Press Ctrl-Z: it doesn't make the armature parented to the cube again.