song authorization

there are certain songs I paid thru Itunes and some of the songs I cant play because its telling me that my computer is not authorized to play this song. My computer is aurthorized but still telling me that this song is not authorized to play on this computer. So I deauthorized my computer and the re-authorized it again and still telling me the same message. So I dont understand Itunes is not on the same page. I cant play it on my Ipod Touch. Same message