I hadn't changed any preferences like you did, but I'm experiencing the same thing. Hitting pause doesn't work, Hitting space bar doesn't work. I will note that playback does stop about 50% of the time, the other 50% will keep playing despite trying to stop it. By accident, I found out I could stop playback by manually saving the project (file-save) with my mouse and it stops. Hope that helps. Not ideal, but until the bug is fixed, it's at least a work around. ... View more