[OS X] iMovie 11: Choppy video when editing I was wondering if anyone knows what can cause choppy video in the preview window when editing an HD video in iMovie 11? The first second of the video plays and then gets real choppy. I looked at the Apple support forums and I really didn't see anything that pertained to my problem. If I play the video back full screen it is fine. I also have issues when scrolling through the added clips in my project. I have rebooted and made sure no errant processes are running. I am running OS X 10.8.2 on a 2010 MacBook Pro (core i7 with 8 GB RAM and 128 GB of free hard drive space). I even turned off automatic graphics switching and verified that it is using the NVIDIA GeForce GT 330M graphics card. I've edited other video recently (since going to 10.8.2) and I've had no issues. Any thoughts short of reformatting and starting over?