there will be a native means for writing the tags in the next client release and using the files released after 5.572 (and sort of lost by the forum upgrade) aren't really recommended and you'll have to wait for the next client release (no eta on that).
also
http://forums.winamp.com/showthread.php?t=317153 may be off use if you're experiencing data loss issues (though that then leads to fact that the player shouldn't be unstable as it's not for most users).
-daz