I have a similar setup with a similar Sammy 32" HDTV. Occassionally I have the same issue. But a re-boot usually fixes it. Not so with yours?
Also on my Sammy, it is required that I use HDMI 2 for proper sync between HDTV and graphics card. But I'm using a DVI output on the card w/adaptor to HDMI because I use a 2.1 speaker system and need no TV audio.