There are lots of homes that don't have grounded outlets. Anything built in the 1950s or before won't have them.
What I think is happening here is that the cable coax shielding is always grounded at the entry point to the house. If an outlet is wired backward, you could see voltage between the supposedly neutral side of the outlet and that external ground connection, and that could have fried the cable box.
Use one of the plug in testers, and if that indicates a reversed connection, check the outlet first. If that's wired OK, you'll have to go back to the breaker panel and check connections there at the breaker for that circuit. The breaker should have the black wire, and the white should go to the neutral bus.
Seeing you have some knob and tube work, the neutral and hot could have been unknowingly transposed in some other place. If that's the case, the simplest fix would be to flip the wires in the outlets.
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