By way of an update, I’ve tested the Decklink card with an HD component feed from my camcorder with no problems. Also I’ve tested the HD component feed from the PS3 into my TV without any problems. It’s only when I send the HD feed from the PS3 into the Decklink card that everything goes blank..
Could it be that the PS3 ‘sees’ the Decklink card as a capture device and blocks the HD signal???