I don't understand where the copyright issues are. First you have authorised the machine, then identified who you are. That pretty much says that YOU can download on this MACHINE what you have already PURCHASED. Unless there is something that is much more complicated, I don't see the problem. I can sense this is a music industry issue, because if you can redownload a book, why does copyright not apply here as well.
So my take, it is the music industry. If it makes anyone feel better, my backup as well as the original media folder got corrupted, no I lost the music. Funny enough, iTunes can see that I have purchased it, but i can't repurchase it. How contentious is that