iMovie is basiclly a gateway drug of DV editing. After a while its performance doesn't please you as much as you would like. Apple's plan is for you to start using the big boys *cough* heroin *cough* Final Cut Pro. Thats why you hear little audio blurps and messed up preview windows. It's the little things that'll make you switch over (which is a good thing).
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-Bizzare
Specs: PowerBook (Firewire), 500 mHz, 256 MB RAM, 18 GB HD, AirPort, OS 9.0.4