I've finally managed to get an Apple ATI Radeon X800XT (here, the guy seems to have some more in stock, and accepts a less costy offers than the card is listed), as an ultimate upgrade for my G5. But my joy didn't last long. Sometimes (not always) the computer hangs at startup. The grey screen shows up (refreshing slowly), even with screenbar present and that's all. Only hard reset helps. Then there's a second issue - sometimes the system boots, but there are artifacts present - in a form of horizontal, multicolour lines that float over the screen from left to right. The effect doesn't fade with time, and sometimes the display goes black for a second. When I reset the machine everything goes back to normal, no artifacts whatsoever.

I've bought the card as Radeon X800XT, but OSX (yes, it boots and works without any problem) says it's X850XT. It's connected through ADC to an acrylic Apple Cinema Display 23" running at 1920x1200.

Any help appreciated.