Um… I run a PC, Quad Core Opteron 2.40Ghz, 8 GB of RAM, NVIDIA Quadro FX 570, 64 bit system, and I have this same exact problem! Everything is up to date on it, when I tested before final install of my user (at work), it handled over 1gb/16bit images like a charm. Now suddenly everything is acting up, rebooting and changing performance settings do nothing! What am I supposed to do?