Debian AMD64, fglrx-driver
Broken: 2.72 and later
Short description of error
The GGX distribution on the Glossy, Glass and Refraction Nodes produces black pixels in some cases.
The roughness value seems to play a major role.
In this picture it produces black lines:
Exact steps for others to reproduce the error
Here is a .blend file:
I'm changing the roughness value, which depends on a noise texture modified by the formula e^(x*y). (x is the noise texture value, y=-10)
Open in 2.71 and in the current version. Set viewport to "Rendered" and you should see the difference.