I recently was given a DVD of a live music performance to edit. For some reason, the audio and video were out of sync by about 1/4 second. After spending a bunch of time trying to find a fix for this (I use a Mac), I ended up simply exporting the audio track as an AIFF file, deleted the audio from iMovie HD6, added a quarter second of silence to the audio file in Audacity, then re-imported it back into iMovie. While not perfect, the video is certainly better than it was. If anybody knows of another way to do this (again, on a Mac), I'd love to hear it. Thanks!