ir2020 blank screen after power save

Hi all.

I have a Canon that, when left overnight, has a blank screen in the morning. The op panel is lit, so it's getting power but none of the buttons or the touch panel works. The only way to get rid of it is the power the machine off/on. Then it works fine after that.

Any ideas what this might be?

I'm a Ricoh tech and I don't have much experience with Canon equipment.