The culprit is my ATI Radeon x1900 XT. I've cleaned off all the dust that was caked in the vents....which is every 4 months. It's irritating. But even once cleaned, I still get the horizontal lines. After a while, the Mac Pro locks up.

So...my question is : what video card should I get to replace this? Remember, I have a 2006 Mac Pro (Intel chips)

I've read the internet and people have run into this problem. Firmware updates didn't work, I've tried it.