**System Information**
Ubuntu 14.04 64bit, GTX 570
**Blender Version**
Broken: 2.74
Worked: -
**Short description of error**
I render the image sequence in .png format using terminal command "./blender -b {scene file} -a" and use multiple terminals and multiple computers to speed up the render time. The folder is on another harddrive which is WD My Book Live 2TB. All computer were connected via NAS. The result is some of the .png files randomly couldn't recognized by nautilus thumbnail and resulting in black preview on Blender VSE after editing. I'm using Blender Render and Approximate Occlusion feature.
I attach the preview thumbnail in nautilus; the "broken" file (file number 0147.png); and the correct png file (file number 0148.png)
{F167293}
{F167295}
{F167297}