This problem just started today. I added a few new songs to a playlist that was already on my iPhone. Once the syncing was finished I went to play one of the new songs and there were red stop buttons next to all the new and recent tracks (songs that I had added a few days ago, which were playing previously). I tried rebooting my phone, deleting the playlist off my iPhone and then re-syncing it. I'm not sure what the problem is but it is extremely annoying. Any suggestions?