Things to help narrow your problem:
Disconncet all other AV connections from the back of the Tivo (only hdmi plugged in).
Try another hdmi device on the Tv (dvd / bluray player).
Try the Tivo on another Tv.
Hard reboot both the Tv and the Tivo (pull power cord for 10 seconds).
Factory default the Tv (see user manual for your model).
Update the Tv firmware (see Sony support site