I have found that the secondary lightbox does not work at all for any video content in Safari 6+. I have tested it on multiple computers. Safari 5 or earlier, my videos play fine.
Here's what happens:
I'm confident it's not an encoding issue because videos load without a problem in Chrome or Firefox.
There are no additional plugins installed that could interfere.
Any ideas of why this might be happening?
Here is a sample link that won't play for me in Safari 6.0.2.