I have the same issue. I'm in Westchester, NY. Lost most channels above 49 at 12:04 AM. Looking at Verizon's Support Twitter accnt (@VerizonSupport), most users reporting FIOS TV channel problems seem to be in NY. So far Verizon itself has not reported anything... Why have a twitter feed if you don't use it for timely updates, Verizon?
Finally got a message from Twitter@VErizonSupport (DM) and finally got someone to pick up on the phone.
All they know is that 483 channels are down. They have no idea how long it will be down, they have no intention of posting any public announcement for "security" reasons. Can you believe that???
Same here at 5:00AM today in Staten Island NY. It first said "incompatible audio signal" and I went crazy trying to see what was wrong. I was about to start changing inputs on my Sharp but I knew they weren't wrong. Rebooted several times. And then called tech support to find out that most channels were out.