Can't find "Unlock Audio Clip" option in iMovie HD 6.0.3
I'm attempting to make clips from a number of not-so-well-made DVDs on which the video leads the audio by approximately 1:10. So, I did the obvious: I chose "Extract Audio," selected the audio clip, and used the arrow keys to shift it left by that amount. The problem is that I now find myself completely unable to rid myself of that unwanted 1:10 of audio at the beginning of the clip. If I split the clip at the beginning of the video and attempt to remove the audio-only portion, iMovie warns me that this will invalidate one or more audio locks -- and if I proceed, the tracks get right back out of sync again. The same thing happens if I move that portion out of the timeline and into the Clips pane (though without a warning in that case).
From what I've read so far, there is supposed to be an Advanced->Unlock Audio Clip option that will solve this problem, but I'm quite certain that I've never seen it. My Advanced menu has only four items: Extract Audio, Paste Over at Playhead, Lock Audio Clip at Playhead, and Revert Clip to Original. This doesn't seem to change regardless of context or preferences settings.
I've been browsing the support area and Googling like mad and generally trying to figure this one out for at least a couple hours now. I suppose my next step will be to export the clip as DV, import it back in, cut the first 1:10, and export again. Still, given the amount of content I need to fix in this manner, that's going to get extremely painful and time-consuming, and clearly there must be a better way. Can anyone help?
MacBook Pro, Mac OS X (10.4.11), iMovie HD 6.0.3