OT- iTunes/iTunes store question?

I don't use the iTunes store very much but earlier this year I got a few iTunes gift cards for my birthday so I decided to spend them very wisely... on some Melodic Rock, of course!
I got Danny Vaughn's Traveller, Line of Fire, and Bonrud.
HOWEVER, just the other day I was feeling some LoF, and I went to go jam out to it but all of a sudden my iTunes had something pop up saying my computer was unauthorized to play this file?!
I was curious, and tried every song from every album I had iTunes'd and none of them would play due to the same reason. How could this computer (the one I bought the music on) suddenly be unauthorized to play the songs? I'm pretty confused and miffed right now and any help would be killer.
I got Danny Vaughn's Traveller, Line of Fire, and Bonrud.
HOWEVER, just the other day I was feeling some LoF, and I went to go jam out to it but all of a sudden my iTunes had something pop up saying my computer was unauthorized to play this file?!
I was curious, and tried every song from every album I had iTunes'd and none of them would play due to the same reason. How could this computer (the one I bought the music on) suddenly be unauthorized to play the songs? I'm pretty confused and miffed right now and any help would be killer.