Some of this blurriness is inherent with Standard Definition signals.
With the upconverting DVD player, it's hard to tell since you've correctly set the output resolution. AMP settings to off will turn off the processing (except to upconvert the signal to 120Hz and 1080p). This processing may be causing the issue, and if that's the case, you might try changing either the Entertainment Mode, or enabling "Just Scan" settings (in the manual).
With the cable, it's a little more difficult to diagnose. So if you can get the DVD upconverter to work, you've solved one problem.
The problem with cable is that the digital signal is compressed (zipped), which while blurry motion shouldn't occur on the forepicture (ie: football player), it could very easily happen on the background picture (blurry grass or crowd). Since it varies from content provider to content provider, it's hard to determine that.
But if you can't adjust the picture for both the upconverting DVD player and the cable box, then it may not be something that will work for your situation.
How does it look when you're watching HD channels and signals?
I purchased the Samsung LN52A650 two weeks ago. I connected it to my comcast HD box via an HDMI cable (outputting 1080i). I also have a Samsung upconvert DVD player connected via a HDMI cable (outputting 1080p).
When watching standard definition cable, HD Cable, or DVD movies such as (sports, movies, kids cartoon shows, news, etc...) and there is any of the following :
1) movement on the screen (Face turns sideways, or hand movements),
2) movement accross the screen (person walks from on side of the screen to the other without the camera panning) or
3) movement where the camera pans to try and follow the moving object
the screen gets extremely blurry and it takes the TV a second or two to clear up. I've tried setting the AMP to off, low, med, high, but the problem still happens.
I also get a random studdering effect of players when watching sports.
I contacted samsung and they sent out a technician who replaced two boards on the tv (Main & T-Com) but problem still occurs.
I currently have the AMP set to OFF as this reduces the TV from trying to smooth everything further. With it on the blurring was worse and made the picture look fake to whatever I watch.
This is making me sick to watch such a beautiful TV perform like junk. The blurring effect makes me and my wife dizzy and hurts our eyes because we try to focus, but it's the tv and not our eyes.
Is there any known problems with this tv or other settings/firmware updates that I can do to get rid of this, otherwise I may have to return asap.