[MacDV] Authorizing iTunes purchase for my computer

[Donald Tully]

Hi Listers - I need a little help, please.  About a month ago I made  
an iMovie project using legally purchased and downloaded music from  
iTunes.  I burned the project with iDVD and all was well.  Today I  
made some changes to the project and attempted to burn it again using  
iDVD.  An error message told me that I needed to have the iTunes  
Store authorize my computer to use the music.  Being the compliant  
guy that I am, I said sure. But even after I went through the  
authorizing process, I was still not able to use the music with my  
project.

Can anyone tell me 1) Why do I have to get "authorized" to use music  
that I purchased (Same computer used to buy the music and make the  
DVD. and 2)  Why won't the music that I purchased and then authorized  
work with my project now when it worked fine with the original  
version of the project?

Thanks in advance...