Do you know what BIOS version your board has? You must use version 3.20 from your board's download page, for your IVB-E CPU to be compatible with your board. There is also a different INF/chipset installation program that must be run, and a new version of the Intel IME software that must be installed.
If you did all this already, there may be a problem with that BIOS update, or an unknown compatibility problem with your video card.
The D6 error you have is: No Console Output Devices are found, which means a video source failure. Currently setting the PCI-E speed to 3.0 causes a failure of the board to communicate with the video card.