Interference with G5 and ATI Radeon 9800 Pro

I've never been able to get a clean component signal in or out of my G5 with the Blackmagic Decklink Extreme.

When I contacted blackmagic they sent me a new card (after a bit of haggling). After the problem didn't change it was suggested that I move the Blackmagic card away from my graphics card (an ATI Radeon 9800 Pro). This changed the nature of the interference (faint digaonal lines) but didn't clean things up. I've moved the blackmagic card to all three available slots in my machine and each produces a different interference.

It seems to be a known problem, since Blackmagic suggested I try moving the decklink, so does anybody know a solution? The decks and patchbays involved work perfectly with other systems and the decklink does work perfectly with composite or SDI signals, but since most of our work is still component, I need to find a solution.

Thanks,

Adam