Unavailable tracks in iMovie? Why? Can anyone help me understand?

[Howmander]

So I was editing in iMovie on my iPad and going through my music and there were a few tracks that were greyed out and said "Unavailable" in brackets right before the title. I knew they were part of a free iTunes sampler I downloaded, so I figured that music downloaded from iTunes couldn't be used for iMovie projects, so fair enough, that's understandable.

However, as I was going through the list, other songs I KNOW I downloaded from iTunes both via individual purchase and other free itunes playlist giveaways were in white and completely available for use in iMovie. (as were all the songs I ripped from my CD's myself) so I wen through the list and EVERY album and song were available EXCEPT the ones from the "iTunes Fall 2009 Sampler" playlist giveaway. Every ripped song, every purchased song or album, and other free itunes playlist giveaway all work, so does anyone have any idea why this one particular album sampler is not? Any idea what I need to look for, where to look in the file, or what to change to make it available? If you can shed any light on this, I would really appreciate it.

EDIT: I hate how the forums automatically generate tags, but then when you hit submit, it won't let you post because the number of allowed tags are exceeded: Stop generating too many tags! yeesh!

[Howmander]

So no one with iMovie has come across this problem at all?