BigB,
I have a computer monitor that did the same thing, is the TV you have on the same circuit as a single phase fridge or things that have a high starting current?
If that is the case, newer TV's are a lot more sensitive to voltage drop and a reasonably large motor start current will cause that "drop-out", until the appliance current evens itself out.
What I did with my monitor was bought a small 1:1 isolating transformer (enough to run the monitor) and the problem disappeared, because as a rule, a voltage transient will not go through both sides of a double wound transformer, the hysteresis in the core should smooth things like that out.
