There's something really wierd going on there.
I cannot find any relationship between the parts of the frame being affected and the content. Is this artifact consistant regardless of movement?
I'm really grasping at straws here though.
It looks like some bad interlace artifact that you can get when down scaling badly however that affects areas in motion and if the leg is moving all of it should be affected.
I've certainly not seen anything like that in V8 with HDV, just the usual crashes etc so I only use it when I must e.g. for XDCAM.
Something along those lines would kind of explain those wierd artifacts. It might have been a clue if you'd mentioned you were using a CF codec and not native HDV.