Running iMovie 3 on an 800mhz iBook. 640 RAM. I place clips on the the time line and when I play them back there are frequent jitters. I'm usung QT 6.5. Do they go away when rendered? I'm new to this whole mac thing and bought one for itunes and iMovie specifically. I was assured by salepeople that the iBook could handle iMovie, even though a PB would do it better. But really, I'm just doing home movies -- or trying to anyway. Thanks.