Tested with Ubuntu 14.04 and a GeForce GTX 1080 Ti as well as Windows 10 and a GeForce GTX Titan X
Broken: 2.79b (official release), 2.78c (official release)
Short description of error
Activating / Deactivating of the "Speed Vector Pass" in the renderlayer causes a different motion of a IK Bone.
If the "Speed Vector Pass" is disabled, the rendered results are consistent to the animation shown in the 3D view.
The only difference between the attached images is checking/unchecking the "speed vector pass".
Exact steps for others to reproduce the error
Open the blend file
Render Animation with "Deliver speed vector pass" of the RenderLayer enabled / disabled