System Information
Windows 10 Home across all machines. NetRender ran on all previously on 2.78c.

Blender Version
Broken: 2.79 RC2 "7b397cd"
Worked: 2.78c

Short description of error
Network Render fails to finish renders. The BMW render completes, but produces a pure black .exr file and no output in the "show render" part of the online network render controller.

Exact steps for others to reproduce the error
Download the BMW benchmark, and Blender
2.79 RC2, set up two machines, one running Master and Client, and the other running slave. This configuration worked before in 2.78c. Render the BMW benchmark from the slave through the network after connecting. Render will show up as "done" in the online browser, but the exr of the render you can download and the "show" option show no render.

This behavior was also seen on 2.79 RC1.