Problem playing one of my iTunes store purchases

I recently purchased a song from the iTunes store. When I try to play it in iTunes on my PC, I get a message that I need to authorize the computer. So, I enter my Apple ID and password. It tells me that the computer is already authrorized, which makes sense since I am able to play every other song in my Library. It says that my computer has been re-authorized and is one of three authorized computers. I then try to play the song again, and I get the same message - that I need to authorize my computer. I do it again and get the same message. This just keeps repeating. Why can I not play this song that I purchased on my computer? It plays on my iPhone.