Last week I ordered an ATI 5770 card from the Apple Store to go in my 2008 Mac Pro (3,1). The system software is OS 10.6.8. I also ordered a MiniDV to DVI adapter so I could run both my 23" ACD's. But I had to pull the card because it seemed to be causing problems. At one time or another I would experience the following: Upon boot, the system would fail to recognize RAM installed on riser B (I have 14GB total: 8 on A; and 6 on B) Or the system would fail to boot - just the black screen When the system did boot, the second screen would be black (from the DVI connector) At other times, the system would fail to wake from sleep, forcing a re-boot At no time do I recall experiencing a smoothly running computer with the 5770. I don't think it ever recognized the RAM on riser B. Then, the other problems occurred, with the last being the complete failure to boot. Once I replaced the 5770 with my old ATI HD2600, everything was back to normal, running both my ACD's with all 14GB RAM available. Any thoughts? I can return the card to Apple, but if I can get this card to work, I'd rather keep it.