[johnnym]

I am sad. =(

I can fully understand that.

Does it work again after it was powered off (plus removing power and hitting the power button to "empty" the PSU) and has cooled down for an hour maybe?

When you decide to exchange the graphics card, you could in between try to run the machine when the possibly faulty graphics card was removed, to see if that error is still there. Which if still there would rule out the graphics card IMO.