Hi guys, After reading these threads, I ordered a 'flashed' GTX 570 to speed up my CS6 work. Unfortunately, although my system boots up nicely with the card, after a while (sometimes within 30 seconds after boot) the system simply shuts down (immediate black screen). Rebooting isn't possible, unless I unplug the power for at least 10 seconds. Is this the result of a PSU not giving enough power, a driver issue, a faulty card, or is something else going on that I'm not aware of? The threads I mentioned claim that a GFX570 1.3GB model doesn't require extra external power, as it should get enough power via the two 6pin mobo connected cables. I have all the lastest OS/Cuda driver versions installed, and my system currently has these internals: 14 GB ram 4x HDD 1x SSD 1x LG Bluray 1x eSATA PCI card As a test, I got a Quadro 4000 from a friend (which is supported officially by Apple), but it also results in the same crash. It seems like my MacPro simply doesn't like Nvidia cards When put back the basic ATI Radeon HD 2600 card, then no crashes occur at all.