Put bluntly, Doubletwist is a lousy product. I tried it last winter then uninstalled it. Tried it again last month and then uninstalled it. I don't know anyone who has success with it. It takes forever to scan my computer for songs with the I-tunes playlists. The sync process locks up and doesn't transfer all of my files. I've tried every possible solution, including uninstalling and deleting all related files and folders from my computer. Still no luck.
Right now I'm using Windows Media Player. It is not as elegant as an I-tunes related solution, but it works.