I'd give TiVo a call.
I don't see why they wouldn't support the AFN, that's just unAmerican.
Zap2it has the AFN listed as a provider, TiVo and Zap2it both use Tribune Media as their program guide source.
I found the AFN on Zap2it by inputting 10101 as the zip code.
Panasonic Viera TH-46PZ800U 46" Plasma HDTV
TiVo S3-65 HD Hours-Lifetime
TiVo HD 20 HD Hours
TiVo Roamio Basic 300 HD Hours-Lifetime
Harmony 880 Remote Control