Error downloading song ? Won't play, can't buy it again, won't delete.

I was downloading an album today and on one of the songs an error box popped up. It said something about there beign an error of some sort while downlading one of the songs. The song says I have it in my Itunes store but it my library I can't click on it. It also will not play, even when I click on it in the store. Itunes won't let me purchase it again and it also won't let me delete it. What am i supposed to do? It frusterates me how I payed for a song that I can't listen to, and I can't even re-buy it to see if it will work.