I was having a lot of problems with my HD channels and just thought I would post that they are now fixed, and have been trouble free for 4 days now. Maybe will help out some people?
First here were my problems:
1. Picture breaking up on many HD channels, eventually leading to "Chanel Unavailable" message.
2. Replaced HDMI with Component cables with no change. Now running on HDMI again with no problem.
3. Problem on all receivers in the house, 1 HD-DVR, 1 HD-Receiver.
We had Verizon service come out 2 times to fix this. The first time they cleaned up some wiring, removed some extensions etc. They also said our signal from the box to the recievers was too "hot" and that could corrupt the signal. The problem went away for about 6 hours and then came back.
The second time we got service the new guy said our signal was still too "hot" so this time he replaced our FIOS box outside the house, and dialed the signal down a little more. Since then we have had no channel breakup, and no channel unavailable messages. So it seems our problem was related to faulty FIOS box outside the house that feeds the recievers.
I am not saying that this is the same as the problems other people are having, but if you have symptoms similar to mine then you might ask your service techs about it.
Since we have had the issues resolved I have finally been able to enjoy the FIOS service, and I think that it really is the best TV service you can get. The quality is excellent and even though it's not TIVO the DVR is very good.