Since there is no "help" forum I have no idea where to post this...

I had a freeze/graphic glitch with a game and had to kill X with its shortcut, after which this problem started. Now almost every area of the screen where transparency is involved will instead render pitch black. This includes the area Cairo-Dock and it's icons and text displays as well as my panel and K-menu when using transparent theme, as well as the little areas "cut off" from the rounded corners of the Breeze themes. Oddly enough, the Analogue Clock desktop widget renders OK...

See this screenshot: https://www.dropbox.com/s/fc53q4db7yssp ... 3.png?dl=0

I reinstalled several packages hoping it may fix it, including opengl/mesa/libgl packages, gtk2 and 3 packages, plasma, nvidia drivers and Xorg, to no avail. Needless to say full reboot and system upgrade didn't help either.

I'm pretty annoyed and frustrated because something clearly broke and I have no idea what to do...

Any ideas?

Alright, so this issue got resolved on its own.

What happened is that the flag "IsOpenGLUnsafe" in my ~/.config/kwinrc has been set TRUE by the system after the VGA issues, which effectively disabled compositing. After setting the flag back manually (and replaceing my faulty VGA) everything works as expected.