Missing several songs from a purchased album.

I'm in the US and trying to download an album I purchased previously.

In my "Purchased" area of the store, I can see the album, but I only have access to tracks 4, 6, 9, 12, 13, 14, 15, 16. I purchased the complete album, and I can see that on my purchase history.

If I search the iTunes store, I can still find the album, and it has the full 18 tracks that I *should* be able to download.