Originally Posted by dunnery
I'm sure it's not just ardour that does this.
If you haven't observed it with any other application, then you can't be sure it isn't ardour. When this problem happens, can you do CTRL-ALT-F1 to get to a system terminal? You'd use CTRL-ALT-F7 to return to the graphical display.
If you can get to a system terminal, you can log in and kill the ardour process and then return to graphical and see if the mouse and other controls problem is still there versus not.
I'm unfamiliar with both that particular distribution form of Ubuntu as well as ardour, but it may be that it was designed to behave that way because the intention might be to have a kiosk like/jukebox interface where the users of it can't play around with other apps or system settings while the media app is running.