If you google it, you'll see it's a common problem with FiOS. My guess is that BrightHouse doesn't have the same codecs with it's cable box as Verizon does. Also, you're using a receiver that can decode everything. There's a fix for it but you have to switch to PCM.
http://forums.verizon.com/t5/FiOS-TV-Technical-Assistance/HD-boxes-dropping-sound/td-p/179283
Power off the Set top box.
Hit Select
Hit Menu
You will see a white screen and an all text menu called USER SETTINGS. Use the arrow keys to move around.
Scroll down to a line that says "ADDITIONAL HDMI SETTINGS" and hit a right arrow to get into the next level of the menu
There is a sound setting called AUDIO OUTPUT It says AUTO Scroll to it and change it to L-PCM.
Exit out of the menus, power the unit off and power it on again.
Even though there's a work around, I think it's pretty shitty as I assume that means that the TV can't properly handle Dolby Digital?
edit:
Holy cheapskate corner cutting batman! After a quick google search, even the Vizio sound bars don't support Dolby Digital! Tons of bitching on Amazon reviews about it. Then I found this one that DOES support Dolby Digital but doesn't support DTS!
http://thewirecutter.com/reviews/best-cheap-soundbar/
My point is, don't buy a Vizio. They aren't even that cheap anymore anyway since everything is so cheap. This could be a case by case thing with Vizio. I did look up your TV's manual and saw some reference to Dolby Digital (didn't read the details) couldn't find anything on DTS.
Sounds like a Fios issue tbh, Verizon is pretty assine with supporting everything (Look at the nexus tablet hubbub even) The TV itself doesn't support DTS however...its kind of expected. Thats what a good sound card, or receiver is for. Stock speakers dont have enough range to make difference. The TV has Dolby Digital PLUS not normal DD, DTS Caps at 1.5MBps DD+ 6MBps DD+ Supports 13.1 audio channels. Then we have Dolby TrueHD which isnt present on this
There are some cheap $100~300 Yamaha recievers that have full Dolby modes & DTS:NEO Available aswell DTS-HD even caps out at 8 channels at 1.5MBps...
So... Dolby Plus kind of theoretically nukes it. I always keep receiver on DD+.