Why locking?
The "locking" problem was happening to me in iMovie as well. You're right. It's not obvious and I don't understand "why" anything should be locked. I've found iMovie and iMovie HD to have quirks where they fail to do what I want them to do via drag and drop and that means som property isn't being satisfied. And it's up to the user to figure that problem out. Since I only make movies about once a year, I forget how I overcame the problems the next year so there is always a re-learning curve to these applications. :-(
Back to the locking problem. So I moved the locked section to a small portion of my clip, and then I was able to drag and drop the title to the unlocked portion of the video. I tried to do this a THIRD time and couldn't do it no matter where I put the locked portion. So I then selected the portion of the clip, with the beginning of the selection the location of where i wanted to put the title, and the end being the end of the clip, and then edit->split to creat a split. Then I was able to add a third title and do more work.
This iMovie/HD software is so frustrating because it STOPS you from doing work and you have to guess and fight with it to continue. I have no idea why it does this! Is it buggy or by design? Oh, sometimes shutting down iMovie and then starting it again will solve problems to.
Maybe someone could explain the idea behind this behavior. I invite you to defend why these problems are features rather than bugs. 🙂
😕