Not sure what happened here but I just battled this thing. I normally use FF and Chrome. Everything was along ok adding songs until I got to add #11. It added the song in the middle of my playlist. I deleted it and added again. Tried it in Chrome. Thought it might be the lack of a price on some tracks as it was sticking it in as the first track with a price but even given everything 0 or a value did not fix in FF. Punted to IE and it actually worked. Write it down IE is good for something. I had done some customizing to remove the RATING but I put all that back in and was still having the same problems in FF until I went to IE. Put that on your list of stuff to look at.
I like the plugin. Getting it to be able to display ARTIST specific playlists on the same page would sure be sweet. I have a musicians I would use this for who have multiple albums in their store and we don't really want a page per album. You know what I mean. Thanks!