I had an issue after I just installed 8.1 when my pc rebooted after the update my pc went to a black screen.
I didn't know what the problem was, so I downloaded and updated my bios to the latest version, I removed my discreet card and the pc booted successfully with the onboard graphics.
I found that Lucid Virtu and the iGPU was the issue. I uninstalled Lucid Virtu MVP, and disabled onboard graphics in the bios, shutdown and re installed my graphics card, and it successfully booted.
Theres an issue somewhere with the Intel HD graphics driver and the use of Lucid Virtu MVP when you attempt to use the igpu and your discreet graphics together as multi gpu.
This is what I encountered and what worked for me.
I am only running my 680 now and have the Intrel HD graphics disabled. Hope this helps anyone else that may have the problem I encountered.