Tivo Roamino been work great for 2yrs, now I am getting almost every day in the morning, the "V58 Channel Noth Authroized" error. A reboot of the Tivo fixes the problem for 24-48 hrs, then it's back again.
Your Roamio and CableCard are probably not paired properly to the Comcast system. Call them up, or 'chat', and they should be able to get it cleared up.
Looks like it is an xfinity problem. I have done nothing and zero V58 error for the past 3 days.