iMac (Retina 5K, 27-inch, Late 2015) I have tried on older macs as well.
2.77, even tried of 2.74
Short description of error
After a complete render, the file (quicktime) - (h264) is only playable through playing the preview on finder. Played on quicklime it is just black. I experienced this error only the last 5 months.
Exact steps for others to reproduce the error
The file is ready to be put on render. it does not matter if full animation is completed or cancelled before.