Although I have not been overly impressed with the TiVo (and certainly cannot see why people rave about a piece of kit that apart from one extra tuner has less useful functionality than its V+ predecessor!), I've not had a problem with it since installation back in April. However I am getting the exact same fault following last night's "upgrade" (I live near Lincoln).
Tried unplugging the box for a few minutes but it makes no difference. Called the fault line earlier and an engineer is coming tomorrow evening. The guy I spoke to did apparently connect remotely to the TiVo but couldn't see a problem in the 30 seconds or so he spent looking at it - must be some pretty nifty diagnostic kit he had to check it out so quickly.
Wondering if I should just get the engineer tomorrow to take the Tivo away and reconnect the V+ box.