Here's the way I capture stills. In the timeline, go to the clip that you want the still from. Once you see the image on the program screen (Single Track), go to File, Export Timeline, Frame. From there you can choose where to save it. For the best quality, I suggest saving it as a TIFF. That way you can import it into Photoshop (if you have it) and converting it into a jpeg from there. You could also save it as a bmp and save it as a jpeg in virtually any photo program. Hope this helps!
Boonedoggle