Yip, add a 'flicker filter'.
Highlight the clips in the timeline, then go EFFECTS / VIDEO FILTERS / VIDEO and chose Flicker Filter. I think deinterlace also works, but hopefully somebody more knowledgable than I pop's along soon to verify that (or the difference between)
Also check the images are the correct size. See Ken Stone's site for loads of good tutorials:
http://www.kenstone.net/fcp_homepage/fcp_homepage_index.html
Powerbook 17 1.67 512meg 100gig FCP HD