Lol, it's definitely frustrating.
So I may have figured the issue out. I did notice that after deleting a few recordings recently, it would still show the icon with a number 1 like I had an unwatched video. When clicking on it, there are no recordings. It's been acting a little weird and the display seems off from the internal database.
For the hell of it I unplugged the external hard drive and restarted the Tablo. It seems to be able to play live TV. I will experiment with the hard drive today.
Maybe it's dying. It's less than 3 years old, and only ever been used for the tablo.
Would nice to get some type of hard drive error in the future, not "error: unknown error"!!!