I read it twice and it sounds like one of the typical crashes. Hopefully a reboot clears it up.
That out of the way you will find folk that want to know why it happens. If you ever find the cause, let others know as they want to know too. So far such seems to be bugs in software and hardware. For reasons of economy, not all things are perfect.
At around 9am this morning while I was playing an online game, my speakers made a buzzing noise (it sounded like it was moving from right to left almost) and my screen made black lines (not dead pixels, almost like a CCTV camera feed)... I looked at my second screen to see if it was doing the same, and I saw a figure that looked like a man moving from one side of my camera's monitoring window to the other side (I was in a skype call with someone at the time) ... I immediately got up and asked people in the house if they had experienced interference on their devices. They said they did not...
I was running camera feed through ManyCam using my android phone LG 3 Beat.
Using AMD Radeon R9 200 Series GPU.
Using 1920x1080 HP V241a monitors.
Using KRK Rokit Sub and Speakers running through a Scarlet 2i4 external sound card.
I am using a 2mbps ADSL connection.
I live in Cape Town, South Africa.
My ISP is Telkom.
I would appreciate any information or comment on what this could have been, as I am scared out of my pants...