Been getting many complaints about the video not displaying correctly on Macbooks. I only have access to one Macbook and could't replicate this same problem on it. The problem might be Flash related. You can try disabling Flash in Safari or Chrome and it will fallback to HTML5 for displaying the video. This will have to do for now until I nail down the exact problem. Mac Users, sorry for this inconvenience. Please let me know if you might have a fix for this issue.
Update: Here's a temporary solution. Right click the video and disable hardware acceleration under settings. This will might cause jerkiness if your CPU is underpowered. Thanks to David Shin for this discovery.