X-ferring mp3's from old computer don't play in frontrow

I just switched from my old iBook to a new macbook, and got all my old data off the iBook, including all my mp3's. I loaded them into iTunes on my macbook, and they won't play in frontrow. They work fine in the standard iTunes window, but whenever I try to play them in frontrow, I get a message that says "this computer is not authorized to play the selected song. Please select the song in iTunes and enter the username and password used to purchase the song." I imported them all from cd's, and I don't really want to go through and re-rip all of them. Any suggestions?