Found another one...it's happened to me a couple of time over the past few days.
When I right-click the grey area of the arrange window (under existing tracks, next to inspector) and select 'add new track' or 'add new track using preset', then I cancel the creation of the new track, Cubase kind of gets lost...
It appears to freeze, but doesn't, it's like the add new track window is lost in the background, and you are unable to click on anything else because you are stuck in this window somewhere that you can't get to. Luckily, I am able to use task manager to force quit Cubase. This also lets you save before the program closes. Then you just reboot the program and carry on.
Doesn't happen all the time but still...bit annoying.