imovie 11 won't play itunes songs

I finished an 8 min movie in Imovie 11 and then moved that movie project to an external drive. Wanted to re-edit it, so moved it back to my main drive where the events and music still were. Now that imovie won't play the itunes purchased music I had in the original--i still get the sound from the clips, but not from the background music. I trashed the plist stuff for imovie...it plays one of the reinstalled songs, but won't play the other reinstalled songs....No idea what to do now.

Any help appreciated. I'm using Mountain Lion with a brand new Mac desktop.