I have the same problem. Tho in my case, 2 out of 5 custom ringtones are somehow not showing under songs, still 3 other does
If i remove em from songs, they are removed from phone as well, and all are in ringtones folder, not music!
Also gotta notice that regardless all the improvements, music on WP (and im on the dev preview) is still crappy done! Instead to be sorted as its pasted, by folders and albums, its messed up by song names.. Seriously, my 10 yo Creative Zen Nano Plus MP3 player cant compare with this lame ****...