Why does fading always looks grainy?
 

I've been using P-Pro for a while. I've noticed that when I fade a clip using key frame handles that I always get grainy / choppy like video on the fade ins and outs. It kinda drives me crazy. Sometimes you see it on the NTSC monotor from the timeline. Other times it's not visable until you play back off a DVD.

Any thoughts? Suggestions?