System Information
Win8.1 64bit | GTX680

Blender Version
Broken: 2.77.1 a506f4c

Short description of error
The pin button in Property Editor doesn't work for bones, both Edit and Pose mode. (Since the message says "Follow context or keep fixed datablock displayed." )

Exact steps for others to reproduce the error
Create an armature, switch to Edit or Pose mode, click Pin button, then select another bone.