Looking for a solution to this, it seems a lot of people have had the same problem. I just had it last night. Traktor Pro 4 went instantly from my favorite to my least favorite software. I started up and opened one of my favorite and most used playlists and it couldn't play file. Tried song after song and tried all my playlists. Everything was gone. I ended up deleting everything and reloading the files and got nothing. I finally uninstalled Traktor and reinstalled. Now, I have the songs but none of my hotcues, loops, amd worst of all, all my stems are gone. That's about 2TB of music I have to go through. Hundreds of hours. Is there a fix for this? Please, someone tell me there is a fix for this.