iMovie Audio Problem - some files won't play while others will.

As stated in the title, when working with iMovie, some of my Audio will play while others won't. For instance, the songs New Soul, Running Hell, and 2 Hearts will play while Eye of the Tiger, Never Give Up, and some elevator music won't. As far as I can see, there is no reason this should be happening-totally random.

And for further reference, this is not an audio importing issue, every song is imported just fine. The problem is it won't play when I am viewing the movie.

Thanks,
Cady

Edit: I am using iMovie 3.0.3, and all files are files purchased from iTunes.