Some receivers require you to assign the component video input in the menu. I don't know if the 661 does, but it might be worth checking out.
My wife is the Harmony guru in our house. She tells me that she can do darned near anything on it, so I would assume you could delete functions from the on-line set-up and download. She also says the Harmony tech reps are nice and very helpful if she has to call about something specific. It might be worth a call to Harmony.