I called support and they sent a repair man out. He wasn't able to do anything (replaced the board, but it was the exact same board/manufacturing date as what I had). So I had to place a second call to support. They tried to get the repair guy back out to fix the problem. I told them there was nothing the repairman could do - it is a firmware issue. But they insisted... The repair company refused to come out again. They 'allegedly' spoke to an 'engineer' at Samsung who told them it was my cable service (funny, I don't have cable...I have DirecTV, and the clip I have on my DVR readily reproduces the problem and, that same clip, shows the problem 'cured'). So I had to pitch a bit of a fit. In fairness the support rep I spoke to agreed it sounded like a firmware issue, but they can't seem to convince anyone.
So they told me they'd send BestBuy the amount I paid for the TV so I could then purchase another. I bought it on sale, and the current Best Buy price is higher than what I had paid before. So that didn't set well with me. So they decided to ship another to me. It should be here in another week or so.
I know it won't resolve the problem though...
But...I did find something else other than 'game mode' that works. The problem with 'game mode' is you turn out being limited on your video and audio settings... But...if you go into the service menu (power off, mute, 182, power on) and set the model number if options to a similar model TV that doesn't have Auto Motion Plus (in my case I chose an LC550), power off and back on again...now turn Auto Motion Plus off (yes, it still shows as a feature even though the model chosen doesn't have it, or that is my understanding). I can then power the TV off and on and AMP really does remain off (no jerkiness to the video on the clip). I obviously can't tell Samsung I did that...of course, that pretty much nails this as a firmware bug since the problem is completely cured by merely changing the model.
BTW, with the model number changed like that I still have the ability to turn AMP on. However, if I leave AMP on Clear and power off/on then the jerky motion comes back again on these clips. So it doesn't 100% cure it...but it at least does allow one to really keep AMP off (and I want to make it clear should someone from Samsung read this - AMP still shows 'off' when the jerkiness appears...but setting it on and back off again makes the jerkiness go away).
Something in their firmware re-enables some portion of the chip that does AMP.
BTW, I do have the latest firmware from Samsung's site loaded.
And please...don't try the model number setting. I will obviously be setting it back to the correct model number before it gets shipped back to Samsung. But if the new TV still has the same problem (and I'd almost bet money on it since they won't believe this is a firmware issue), I intend to set the model number on it and move on with life... And I'll be attaching a note with details of the problem to the TV in hopes that someone that actually cares will find it. I'm certain some firmware developer at Samsung would love to know the details of how to reproduce the problem and how to 'fix' the problem with these settings...and I bet it'd make them say "oh...that's going to be over here in this code...". But unfortunately I don't think such things ever get communicated back to the right people.
So Samsung...if this isn't a firmware issue...then please tell me why Game Mode makes the problem go away. And tell me why changing the model number to a lesser model also makes the problem go away (mostly). Clearly not a signal issue. And it does happen with other stations and with my BluRay. It just isn't quite as easy to reproduce as the clips that have been discussed.