Is there any progress on a solution?
The wife does not understand the press stop twice idea, nor being asked if she really wanted to turn off TV when that was clearly what she wanted to do. Plus, she merely hits the Watch TV button on the remote at the end of the day to turn off the whole system, not realizing that LiveTV is still running, even though the TV and Audio has turned off (I am usually running some background process so the PC does not hybernate). She thinks that pressing one button should be enough (well ... so do I ).
So map the following to the Off button: "Stop", "Stop", "Hibernate" (or whatever you prefer your htpc to do). Then your button will shut down the System no matter if you watch TV or not. Use PS++ and Away mode if you want to stop the PC from hibernating (sleeping, shutdowning) if you record something.