"To remedy this, copy the file "/System/Library/Fonts/Helvetica.otf" to the same location on your ATV."
What location? You din't define which volume you mean here. frontrow? osboot? Since the "frontrow" volume doesn't have a system folder and "osboot"'s system folder is read only, I am a bit confused... Also, I didn't have the .otf font but the .dfont only in my system so I cannot find the specified file. Please, provide further explanations here!