Choppyness when you are playing it back in premiere, or when you export it and play it? If its while your working in premiere, your computer may just not be fast enough, so try exporting it to divx or something and see if it plays fine.
If not, you've probly got some sort of framerate problem. Open your source clip in whatever media player you use, does it look choppy? What framerate is the source clip? Is your premiere project at the same framerate? If not, then thats your problem.