In response to the original poster, I have the Samsung 2796 HDTV and also have the vertical line problem both on s-video and component. I am an anal type so these lines are driving me crazy. I called Samsung in early October and they were not aware of such a problem (or so they claim) but they do have a generous 1-year in home warranty policy so they hooked me up with a local TV repair guy (from Springfield, VA).
This started what has become a 6-week ordeal. The guy came out and thought it was a defective component (I am sorry I dont know what specific component he thought it to be)...so he went back and ordered a new component from Samsung. He came back a few days later and found that it was soldered in (I guess he was figuring it would be pull and replace) and so he had to remove the specific board and bring it back to his factory. He returned a few days later and found that did not fix the problem. So he figured it was another part. Well, it took Samsung over two weeks to mail him this second part--finally got it, installed it and he claims they sent him the black and white part because now my picture is black and white (I find it incredibly hard to believe that there would be a black and white part for such a TV)...But hey at least those damn bars are no longer visible
For the past two works, I have been working with Samsung to work with the store where I purchased to give me my money back (I am past the return date and I threw away the packaging to boot)--Samsung has not returned my calls recently and I am getting a little frustrated.
In the meantime, I bought a JVC 27 inch flatscreen. It really delivers a crisp picture but it had a vertical line of discoloration which is visible on the left side of the screen--which I have also noticed on floor models of the JVC TV so I dont think it is just my TV. So I returned it and got the Sony WEGA 27--have not seen any lines or bars yet although there does some to be a lot of white discoloration (a washed white look) at the top of the screen when I am switching channels--but once the signal settles in, the picture seems fine.
Bottom line: If you are anal about such things, dont get the Samsung--the bars might drive you batty--eventhough they are visible only a very small percentage of the time and otherwise the picture is actually quite nice. My wife thinks I am absolutely nuts and my marriage might not survive if I return the Sony at this point
Peace
Dave