What am I doing wrong w stage size

[SandAttack]

So on youtube and newgrounds I've made 2 animations so far and when I upload them black bars are on the sides. I made sure on my 2nd to read up the correct dimensions for youtube which were 1280x720 px and use them, but I still got the black bars as you can see in my latest youtube video
https://www.youtube.com/watch?v=BzmAFBIta0o&list=UUqycMFkWrep69SFpaw7YcNA

What am I doing incorrectly
(exporting .mov from flash to quicktime, stage size 1280x720 pixel)

[Chocomilk]

I wouldn't export directly from flash. Try exporting it as an swf file and then using swivel to convert it. Flash tends to have trouble exporting video files.

[MarshalBacon]

Check your Aspect Ratio.