I recently purchased a 2009 Mac Pro 4,1 on eBay and its been working like a beast! I upgraded the Ram and Video Card, added an SSD. I was gaming on it last night with my nvidia 660ti just on a simple emulator. After i was done playing i watched some Netflix and went to bed turning off the display on my monitor. (No games were running) I wake up this morning like usual and wiggle my mouse so the display turns on and nothing happens!The computer reboots just like normal, except no video! If i press on the keyboard i can hear sounds from the OS so I know it started up fine just didnt load the Nvidia Driver. I put in the original Nvidia GT120 and that works fine, I'm currently running OSX Yosemite and tried to install Nvidia's new WEB drivers also and nothing seems to work! Non of the cables are bad, the card seems to turn on fine and no super loud fan noise indicating an error. What should I do? Is there any way to reset the Nvidia Drivers on Yosemite? Im guessing this is just a bug with OSX, I highly doubt the video card went bad! I aslo did an NVRAM reset and PRAM reset.