Several Random Purchased Music Not Working?

I went to play a song I purchased through iTunes and when I clicked on it, it just displayed the song for a second and then switched to another. I then tried another song I purchased, but when I clicked on it, it played a totally different song, but said it was the song I played. Some other purchased songs won't even play. Please keep in mind it is just my purchased list (as far as I know so far.) I even tried playing from the normal list and still will not work. Does anyone know how I can fix this? Thanks.

What Mac, version of OS X and iTunes?

Can you do a test on the file, to do that open up Finder and go to where the music is located (usually Music/iTunes in your home directory) and then once you find the music files, select one of them. Hit the spacebar and this should make Finder preview/play the song. If that works, then the issue is with iTunes. If the song doesn't play then the files possibly corrupted..