Hi, After updating to Cuda 6.0.37 and installing Nvidia Webdrivers 331.01.01f04 I could not boot OS X again as the restart, needed after installing the webdrivers, never closed properly (gray circle) and recycled to a proper reboot. Then suddenly, after three times in a row I had to hard-reset my MP with the power-on/off button, I got a reboot with the following screen. The gray bar never ended it's process leaving me with a I then re-booted with my Carbon Copy Clone external back-up/clone and used Disk Utilities to verify my OS X SSD: Strangely the second Verify and Repair - nothing then a trial-and-error - was successful and I rebooted in OS X as expected. Cuda and Nvidia webdriver installed. 1. What was causing this and better how to prevent it? 2. How can I verify that my SSD has survived its ordeal in good health. Thanks for reading. Enjoy your tweakend all. .