I dont know if this has been reported by anyone yet... In RC12, if you attempt to tune a channel in the guide that does not have any guide info, it will not tune the channel. Subsequently, any attempt to tune any other channel (with or without guide info) while that guide screen is up will fail as well. It is necessary to exit the guide and bring it back up again - and then you can tune a channel that has guide info. I've discovered this on channels that have recently been added by my provider, but have not received guide data yet from Tivo.