Make sure you have the right settings in System Settings/Blackmagic Decklink.
Should be Analog Y, B-Y, R-Y and NOT Analog NTSC/PAL (Y in).
Editor
Monitor Flm & Television
Stockholm, Sweden
G5, 2*2.5ghz, 2 gb ram, 600gb Huge raid, Blackmagic Decklink extreme, Apple 23″ Cinema display.