Can tell more on the video card (make and model, settings) and can you tell what Samsung TV exactly? Might help to get a fast and correct answer.
Also the OS of your PC is important. Vista has some restrictions built in with HD content on external devices.
I have a Hometheater PC with a LG Blu-ray DVD drive connected via DVI cable to my Samsung HLN DLP TV. When I try to play a Blu-ray DVD via PowerDVD or Arcsoft Total Media Theater players (both updated for HD content) I get an error that this combination doesn't support HDCP.
My video card states that it's capable of Blu-ray playback. Is there something that must be enabled in the Samsung tv to handle the HDCP handshake?