U3415W, Windows update, black screen

Hi;

So I had a windows update yesterday night, and did it before going to bed.
This morning when I turned on my computer, nothing showed on my DELL U3415W connected via DP to the graphic card. The screen simply stays black and nothing shows up, not even the motherboard logo (impossible to get into the bios).  It is frozen.

So I did some trouble shooting: I unplugged my DELL and instead plugged my TV on HDMI to the graphic card and no everything was fine and ran smoothly. So I then tried using the same HDMI cable with my DELL, and the pb came back, total black screen and can't do anything.
I then reconnected the computer to my TV and tried adding my DELL as a second screen instead, and at the instant I connected the DELL DP to the graphic card, the main screen (TV on HDMI) froze. I could not move the mouse or do anything anymore (note that the screen is not black and simply freezes on what it was showing before I plug the DELL). This frozen state will stay for roughly a minute before unfreezing.
I redid the same thing but tried unplugging the DELL screen before a minute to see what would happen, and everything went back to normal. The computer unfroze and I could use it normally again with the TV screen.

I have tried using and HDMI cable with the DELL, I also uninstalled the windows update, rolled back to a previous version of the graphic card and did a clean install on windows but nothing has worked.

I am really stuck here. I have no idea what to do next T.T
Someone please help me.