That's well known. http://forums.cnet.com/5208-13973_102-0.html?messageID=3364654#3364654 tells about a possible way to handle it. Does it help?
Long story short I'm serving H.264 and x264 encoded mkv's using Samsung PC Share Manager. When I stream to my laptop (connected to the TV via VGA out) everything is copasetic, sound works, picture is good, etc.
When I stream to the TV directly (both are over ethernet so it's not a connectivity issue) the picture looks terrible. It's like all the pixels are in the right place but the motion looks bizarre, almost like a soap opera or handicam. Sorry I can't think of a better description. Hopefully this will resonate with someone who can better explain.
It's a big enough issue that I'm basically obligated to us a laptop until I get the issue resolved.