System Information
Linux (Kubuntu 16.04)
Nvidia GTX 560 Ti

CentOS release 6.8
Tesloa K20m

Blender Version
Broken: 2.78, 2.79rc1

Short description of error

Exact steps for others to reproduce the error
i imported a point cloud from a csv file using this script:

import bpy;
import csv;
def file_to_point_cloud(filename):
    s = [];
    if os.path.exists(filename):
        f = open(filename, 'r');
        for l in f:
            s.append(l.strip("\n").split(','))
    verts = [];
    for p in s:
        verts.append((float(p[1]), float(p[2]), float(p[3])))
    me = bpy.data.meshes.new(filename);
    me.from_pydata(verts,  [], []);
    ob = bpy.data.objects.new(filename, me);
    bpy.context.scene.objects.link(ob);
    return ob;
file_to_point_cloud('data.txt')

Then I added a cube and i created a simple shader with an emission connected to the volume and the density of the emission is link to a point density node.
The point density node is then setup to objects verticies. The objects is the point cloud and every thing else is default.
It renders nothing.
However, when i start deleting some vertices on the point cloud, it starts working as expected.
I added suzanne subdivided 6 times and removed all faces and edges. the point density with Suzanne works.

Based on a (as simple as possible) attached .blend file with minimum amount of steps:
Using the attached blend file you should see the problem. Switching from Particles to Suzanne in the point density node (of the cube).