iTunes authorization prompt

This is the first time that I have used iTunes on my new computer with Vista.
The music downloads and plays ok but when I try to copy it to a CD, I get
this response:
"This computer is not authorized to play or burn this song. Authorizing this
machine to play or burn this song will allow it to be burned". The computer
is already authorzed. There was another thread that mentioned something about
going to Apple to get a patch but I could not find where to do that. Another
thread said that iTunes will not work with Vista. I don't know what is going
on. Please help.