I am beyond frustrated. I own an iMac Intel 2.1 Core Duo machine and I run iMovie HD (6.0.4) for home film editing. I am trying to use the Quartz Composer video effects. The clip previews perfectly. When I click "apply" the red status bar begins and the clip washes out completely, removing the video portion of the clip, but leaving the audio intact. I can restore the clip to original, and retry and once in maybe fifteen tries, the effect will render the clip successfully. 95% of the time, however, the effect washes out the clip to white, leaving no image, rendered or otherwise. I have re-installed iMovie HD, installed developer tools and Quartz Composer, updated all software, and still this happens. What's going on? This computer is less than a year old. Thanks in advance.