I have a MacPro 5,1 with a flashed Zotac GTX 680 4GB. After the Update to 10.9.3 I'm just getting a black screen after boot (after the grey screen with the apple logo). I've installed the newest Nvidia Drivers 334.01.01f01 and CUDA 6.0.46. The monitor is connected via DVI-cable. The Mac is running fine, with the Radeon HD 4870. Thanks for any help.