The same exact thing just happened with the song I've been working on, which is so frustrating. A new bit of information, this has happened to me several times before this update, and it is just the MIDI notes being sent to a different bus. Why does it do this? I have absolutely no idea. It sends my piano to the drum track, my drums are silent, and the lead piano is switched with the piano with delay on it, none of the settings or MIDI inputs affect it. I think this is some larger issue with the update process and trying to open files from the old version, but either way Cakewalk needs to see this. We all have some very important projects I'm sure, and right now it seems like there's no solution.