raino - same behaviour here on affected projects. I just opened a mix this morning of a track I had been working on in 8.5 without issue. This morning the Mute bug is present. The vocal and an organ track which has automation written will not sound. When I load the same project in 8.03 it all works fine. Tried saving from 8.03 and going back to 8.5 but did not fix the problem.