[Unknown bug] Only black color in latest Photoshop

OK, then you monitor profile is bad and you need to replace it. The way to do this properly is to use a calibrator (Spyder, i1 Display, ColorMunki etc) - but if you don't have one, replace the current profile with sRGB IEC61966-2.1. It won't be entirely accurate, but it'll work.

I don't know what you've done, but it probably caused Windows to throw out all profiles and substitute sRGB on its own. So the net result may be the same. But the above is the way you should do it.

Actually I had a hunch it might be a seriously defective monitor profile, but it's not often you see extreme cases like this. If you're not using a calibrator, monitor/laptop manufacturers distribute their own generic profiles through Windows Update. These are often inaccurate or outright broken, but this one wins the price hands down...

Judging by the number of posts recently about this, a particularly bad batch has just gone out from Dell, Asus, Acer, Samsung or LG. Those are the worst offenders.