Can't add songs from iTunes to iMovie

I am having this problem, too, was hoping there would be answers on your post! Did you figure it out?

Having this problem too--iMovie "can't find the original file" while iTunes mocks me by playing it. AAARGH!!!!!!!!

I am getting this also and I have to click on every error message. I can not do anything else or drop out of it. Does anyone know how to bypass these errors? I do have the music on a NAS and that may be the problem, but can you tell iMovie where to look for your music?

Me too. My iTunes library is on an external hard drive. I can't drag songs from iTunes into the "Music and Sound Effects" box.

It would be great if someone could respond with an answer.

so ... over a month later and there's no response.

Have you tried calling Apple?

In iMovie, click the music icon. In the list of iTunes songs, right click the tune and select open in iTunes. Go back to iMovie and try to play it first and it may take several clicks of the play button before that happens. When it plays drag it into iMovie. I got it to work just by luck. It's obviously a bug in iMovie. Come on Apple, let's get it fixed.

I know this thread's fairly old, but I tried everything mentioned here and in a few other threads I saw on the web, and finally I found something that worked: It seems iMovie couldn't access the "main" library, but COULD access songs that were a assigned to playlists, when you select the playlist in the music selection pane. So, I made a playlist called "global" and put my entire library into it. I selected that playlist in iMovie, and now it can find every song I have!