Hi I purchased this tv a couple of weeks ago it is a totally amazing piece of engineering. It is the first tv that has blown me away with picture quality and features. My old sony grand wega just could not fix the tv3 motion judder (csi HD). 
So I plugged everything in I could think of usb stick, usb HDD, network cable. freeview box (just because I had one handy),optical audio cable to samsung hd325 surround amp +hdmi cable, installed the dlna software on my pc. And once I found the allow samsung to connect page in the set policies in the samsung share program, I could now play virtually any movie. I plugged in my hdmi cable to the pc and no signal. a few clicks in the ati CCC and it appeared on the samsung screen. A few more clicks to enable the audio over the hdmi cable, and that was it, however the samsung then would no longer detect the pc hdmi signal "no signal"
I played for several hours but it would not recognize the pc hdmi signal. However my pc could see the samsung as a device and said it was cloned. (my pc monitor is also 1080p full hd screen).
How I fixed it was quick and easy so I am sharing it with you all. I bought a dvi to hdmi cable plugged it into hdmi input 3. When I rebooted my pc I saw the screen appear on the Samsung.  I set up the screen size to 1920 1080 50hz. I then plugged in the hdmi cable from the pc to hdmi input 2. I set that to 1920 1080 50hz enabled sound over the hdmi cable from the control panel. went to source on the samsung hdmi2 was now available I selected it now it is working. 
I removed hdmi 3 plugged in my pc monitor and still the screen stays up on the samsung. job done


Found along the way
sound over a digital pc cable has slight white noise stick with hdmi. 
samsung will not play DTS audio convert it to ac3 using this free program EZmkvDTStoAC3.v12.exe
google it you also need mkvtoolnix and mkvfix. it does not re encode the video so it is pretty quick.


Also it does not support .idx subtitles I used mkvmerge gui to place subtitles in the file. again no re video econcoding so pretty quick.


Set tv motion to smooth :-)
set picture to custom. 
back off the contrast and up the brightness a we bit.
job done 
now to find time to watch the some good hd movies.