Hi, I'm submitting this question in desperation. I was in the middle of synching video and audio clips and was playing them back with no problem. I had done at least 30 pairs of these with no problem, saving the project regularly, and on different days. Suddenly, in the middle of doing one pair of clips, the video started playing back jerkily, as though only doing every few frames or so (the audio is fine). I was working off of an external hard drive attached to a Powerbook (OS X) with FinalCut Pro HD 4.5. I rebooted, checked my antivirus software, rebooted again, but still the same problem, even just playing other projects directly off of the Powerbook without the hard drive attached. In the System Settings->Playback Control, the settings are: RT Safe Video quality: Medium Pulldown Pattern: 2:3:2:3 Play base layer only: Unchecked Frame Offset: 4 I had not changed any of these, at least not intentionally. Can anyone tell me if I inadvertently hit some button that makes the video playback in a halting manner?