Hi pojo,
have you tried swapping the boxes over to see if the same errors occur?
Have you tried a different HDMI cable or port on the TV?
Does this happen on all channels you're viewing, or just certain one. If only a few channels can you list them as that may help ascertain a box fault.
Are you using a sound system of any kind or is it connected directly to the TiVo?
Dave
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali