Howdy all - I want to thank you all in advance for any advice you may be able to give me here. So on with the problem... I have an early 2009 iMac 24 with the radeon hd4850 card. Life was going well until recently when Blizzard upgraded to 64bit graphics. Initially, the machine took it o.k., but was running noticably warmer. Last thursday Blizz did a hot fix restart, and the moment I logged back into the game, boom, instant and total grafic tearing. Entire screen looked like an old-school fractal screen saver. There were other graphic anomallies, like thousands of blackened pixellations at times. Framerates were in the toilet as well. But it was all inside of the confines of the Blizzard game tile. So, must be a game problem... BUT the same thing is happening all over the place now - desktop, opening log-in screen, opened software windows, pull down menus, you name it. Ran the hardware test from disk, complete 2 hr. Version that found nothing abnormal. Tried booting from Snow Leopard dvd and got blue screen of death. Am only in now in safe mode, but am glad to see names next to files again, but have no idea for how long this will work. So any ideas you have are welcome, while I take this opportunity to back up the hard drive. Thanks again!