I have started getting this error on my TiVo since Friday, 6 Jan 2017. It seems to be affecting Tuner 1 so far. From what I can gather the three tuners are Tuner 0, Tuner 1 & Tuner 2. When I switch to Tuner 0 or Tuner 2, they are still ok but the only way I can resolve the problem is to restart the TiVo. Unfortunately, after a while, Tuner 1 stops working again. I only had the TiVo replaced about 3 months ago due to faulty hard disk so I guess I may have another faulty unit. I suppose that it might be down to work they are doing and as usual, haven't notified us.
Error seems to have gone now (although I will be keeping an eye on it). The apparently unrelated fault that Virgin were showing on their Network Status page (concerning Catchup TV) has also been fixed. Perhaps the two are/were related