1. Try a shiny new HDMI 1.4a cable (amazon basics is under 8 bucks here.)
2. Since it's only the fios box, call them.
Just hooked up my lg lm7600 to my fios hd box.
It is flickering or cutting in and out on the hd channels, the sd channels are fine, as are the xbox, and dvd player.
I tried changing the setings on the fios box to 720p, which helped, - it happens less, but its still happens every minute or so.
Any one have a thought on this???