TV Arcs with Cablebox through both Coax and HDMI
Near where the service enters the house, you should see a grounding block similar to this.

The coaxial cable from the pole/dish/mast should be connected to one side, and the coaxial cable feeding to the house should be on the other side. The screw terminal should have an insulated copper wire, larger than 14 AWG, and shorter than 20' (6 m) attached.  The other end of this wire should be attached to either:

The Intersystem Bonding Termination.
The grounding electrode system.
The grounded interior metal water piping system, within 5' (1.5 m) from the point of entrance to the building.
The metallic power service raceway.
The service equipment enclosure.
The grounding electrode conductor.
Or where the building has no grounding means, to an approved grounding electrode.

If the service is not grounded at the house, it could be (and likely is) at a different voltage potential than the grounding system in your house.