Hello Bernie, my name is Dan.
There are a couple of things that you can do.
1) Repair permissions with Disk Utility found in Applications/Utilities. Looks like this.
This is the first thing you do when things don't act quite the way they should.
Not that this is going to solve every problem but it is a good place to start.
2) The next thing I recommend is running Software Update from the Apple menu in the upper left corner.
Just to make sure that your iMovie is up-to-date.
3) I also recommend finding a copy of iMovie HD which is a part of iLife 06.
It was much more stable and easier to use than iMovie 5.
I use these a lot there are some free ones that are okay but I bought several of them and am very happy.
5) The last thing I can tell you is to reinstall iMovie, this may repair what is broken in that transition.
Let me know.