It's called Interlacing. Don't worry about it. Cover the bottom and top of the clips with a layer above all with a small amount of black bar top and bottom only need about 3pixels each end.
If this is for TV don't worry about it. It's normal. If you want it on computer you'll need to crop.
- jon ;)
How many editors does it take to change a light bulb?
www.jonbarrie.net