Using Traktor 4, I recently gridded/cued/organized about 120 tracks, only to have program freeze when I closed it. All my tracks are pathed to my Itunes library. Unfortunately, all too late, I found that the solution was to close Itunes before or when shutting down. If Itunes is closed, the program closes and saves the track collection. Just wanted to share this as I have not seen it listed as a solution for this problem. I will probably right click save my track collection regularly before closing just for good measure.