From time to time, the high definition will disappear from all our high def channels and this has been going on for about 5 yrs. now. I know it's not our tv (which is a 4-yr old Samsung) since blu-ray dvds still play fine. So every time this happens, comcast says no outage we know of in your area; we'll send out a tech. Tech checks every thing out & scratches his head & says, I don't know what to tell you. Last time a tech came out, he replaced all the cables coming into the house. Then in a week or so, the high def will come back. (A friend who lives in the area says this happens to her with her sat. dish--she's been with both Dishnet & DirectTV.) Does this happen to anyone else?