Please answer all questions fully:

what is your graphics card output resolution?
what is your graphics card output refresh rate?
(ie to the LCD / projectors)

what frame rate is catalyst set to?

what is your SDI input resolution?
(ie SDI signal to the Phoenix card)
480i / 480p / 576i / 576p / 720p / 1080i / 1080p

what is your SDI input frame rate?
23.98 / 24 / 25 / 29.97 / 30 / 50 / 59.94/ 60Hz?

How many inputs are you using?

Any other PCIe cards installed?

is the SDI input De-interlaced?

Try disconnecting the SDI inputs
then disconnect the output of the graphics card and re-connect
Then re-connect the SDI inputs one by one.
Does this make a difference?

S