Hi there, I'm having some trouble with rewriting a folder w/ another folder.

I'm trying to rewrite (ex) from: http://mydomain.com/mp3_fold/playlist.php?user=11&id=55 --> http://mydomain.com/mp3_fold/playlist/11/55

This is what I have and getting a 404..

Code:
RewriteRule ^mp3_fold/playlist/([0-9][0-9])/$ /playlist.php?user=$1&id=$2

Thanks so much