I have a Samsung 40" LCD Full 1080p HDMI TV and as of Friday morning started to notice very faint horizontal lines pulsing from the bottom to the top of the tv. they are continuous as well. I've been to many forums and most of the people claiming the problem to be is my cable box not grounded, or it being a "ground loop" problem that would fix this. Now I'm not a very tech savvy person when it comes to HDTV's considering this is my very first. But the first time I noticed these faint lines was while playing my Xbox 360with HDMI cables. I switched to component and they were still there. It's noticeable on the Dashboard and games when it's dark enough to see the the lines. I've talked to several people who claim the firmware updates for my TV would fix this but I am cautious as to whether this will void my 4-year warranty or not. I don't want a run around from Samsung or BestBuy. Any help guys? Oh, and btw, my TV model is the LN40A530 series.
When it comes to cable boxes and consoles, I don't know anything - because I don't have any of them. If the TV can receive OTA DTV in your area, then I would disconnect everything except a pair of rabbit ears (or external antenna) and see if the problem persists.