Nvidia Fermi Sleep / Wake / Freeze Thread I've posted in several places that I had my 550Ti working OOB in Mountain Lion. Well, I see now that it's not true! I am having such severe difficulties that I had to revert to a backup of Lion. Something is seriously broken with this card under ML. I invite you to share your own issues in this thread, but please focus on the *post-installation* experience. Background: My build is a Gigabyte GA-Z68X-UD3H-B3 running the U1H bios, Intel i7 3.4, 8 GB RAM (1333), a bunch of hard drives, native Wifi and Bluetooth, and a EVGA GeForce 550Ti graphics card. Running without a DSDT (the U1H bios doesn't need one), I have my system working *perfectly* in Lion. I am running stock speeds on my processor and everything behaves exactly as it should; it's at least as stable as my actual Apple iMac. Sleep and wake works exactly as it should using USB keyboard/mouse or the power button. I installed Mountain Lion over a working Lion partition (used for experimenting) and after a few hiccups in the installation process, everything was working beautifully...or so I thought. Here are the issues: When the computer sleeps, either manually or automatically, it does not wake properly from sleep. I will get a functional mouse cursor over either a screen of garbage or a black screen. The mouse is not frozen, but I have no system functionality. Console.log is full of Nvidia "exceptions!" and other NVDA errors. When the computer is idle for any period of time, I also get symptoms that appear to be related to the "Fermi freeze" - eternally spinning beach ball with the inability to force quit apps or do anything at all. This requires a system reboot, which then sometimes sends the mother board into a brief CMOS event / boot loop, requiring 3-5 tries before post. Before I realized that there was a major issue here, I had installed over my primary Lion installation, which then became plagued with similar issues. Here's what I've tried: - A brand-new, clean installation on a fresh partition, once with the Nvidia card installed, and once with it removed (using the built in Intel graphics to install). - Booting the computer with GraphicsEnabler=Yes and GraphicsEnabler=No (will not boot with video if GE is set to "no") - Installing updated CUDA drivers (no change) - Toggling the various Power settings on the motherboard (no change) - Testing from the very first boot into the clean install, vs. after installing ethernet and sound drivers individually, etc. (no change) - Installing the Nvidia OpenCL drivers (causes a kernel panic on boot) - Toggling Energy Saver control panel settings (no change) - Setting darkwake=1 (no change) Restoring the Lion system has restored full and complete stability to my system, including working sleep/wake. Can others experiencing similar symptoms post here? I would also be grateful for any other insights / suggestions on how to approach this problem. Many thanks!