Sound cut out of Cubase mid session

I am in the middle of a session and was working in Stylus RMX trying out some sounds while suddenly the sound cut out of Cubase. I didn’t even leave the desk for a break for my machine to got to sleep or load a new plug in, or change anything in Cubase. I was just browsing in Stylus library for sounds.

The only way to get the sound back is to shut down cubase and reload.