@Tarlach: So specifically on your Asus* P8Z77-V LK system, I would recommend currently upgrading your BIOS to the latest version. There has been 4 seemingly important BIOS updates released since the version your dxdiag states. Of those, PCIe functionality, system stability, memory compatibility are listed. A link for that is here, version 1301. Motherboards - P8Z77-V LK
For the Asus* P8B75-M LX Plus system, it appears that the BIOS is up to date already. Could you try doing a full uninstall of all graphics drivers on the system using the below steps? Let me know if it helps.
I'm not sure if it was the BIOS update or just resetting the CMOS, but that did seem to clear up the black screen at login. Odd.
I did do the full uninstall procedure for both PCs when I installed the newer Intel driver. I'm pretty convinced that BSOD is some kind of bug in the 8.1 and later drivers. That PC didn't change at all other than getting an 8.1 upgrade and both PC has have the same BSOD.