iPod help????

Okay, so I downloaded a song from iTunes (Wannabe by the Spice Girls). The first time it took a while to download, but eventually it did. Then when I went to play it on the computer it didn't play and switched immediately to the next song. So I tried downloading it on my iPod and it does the same thing. So a couple days later I bought the same song again. Same thing happened except this time it was quicker to download and it said there was an error. Meanwhile I can download other songs off of iTunes. Then I tried one more time on a different album of theirs and the same song and it did the exact same thing. What do I do?? I really want that song. But if it happens again what do I do?? Anyway to get money back? Not that I really care. But, how do I get the song to play?? (By the way I already tried resetting my iPod)....