Why won't my .m3u playlists from Musicmatch play?

I recently switched computers and am now using a laptop with Windows Vista. My old PC had Windows XP and I used Musicmatch as my media player. I've just learned that there is a "compatibility issue" with Musicmatch and Windows Vista, so I've now downloaded Songbird. Looks awesome... but even though I can import my .m3u playlists originally created in Musicmatch, they won't play. Why is that? Do I need to change any settings? Or is it because these .m3u playlists from Musicmatch simply won't work on Windows Vista. (I spent hours...day actually, putting together these playlists... I would hate to think I've lost all this work - help!) Thank you.